How a City Works

01How cities came to need infrastructure

The short version: Every system in a modern city began as an answer to a specific problem: too little clean water, too much waste, fire, darkness, distance, traffic, pollution, and now rising seas. The answers piled up in layers over about 5,000 years, from brick drains in the Indus Valley to court-ordered sewage plants and flood barriers. Most of the pipes, wires and rules under a city street today date from the 1850s onward, and most were built after something went visibly wrong. Boston, the worked example in this guide, shows up at almost every step.

What did the first cities build?

Cities and infrastructure grew up together. Uruk, in southern Mesopotamia (present-day Iraq), had up to 50,000 residents at its peak around 3100 BC, with another 80,000 to 90,000 people in the surrounding area, which probably made it the largest urban area in the world at the time.⁴ The earliest known examples of writing come from its Eanna district.⁴ Around 3000 BC, Uruk built a city wall about 9 km (5.6 miles) long.⁴

The clearest early evidence of urban plumbing comes from the Indus Valley. Mohenjo-daro, in present-day Pakistan, was built in the 3rd millennium BC and flourished between about 2500 and 1500 BC.⁵ Its streets cross at right angles, with a citadel to the west and a lower town to the east, and it had what UNESCO calls "an elaborate drainage system," along with wells and soak pits for sewage.⁵

The street drains were built of baked brick set in mud mortar and covered with flat bricks or limestone blocks.⁶ Vertical pipes inside house walls carried wastewater down to chutes that emptied into the street drains, and settling pools along the way caught sediment and were cleaned out from time to time.⁶ Mohenjo-daro became a UNESCO World Heritage Site in 1980.⁵

Rome added water at a scale no earlier city had managed. Its great drain, the Cloaca Maxima, is traditionally dated to about 600 BC and credited to King Tarquinius Priscus.⁷ It was built to drain marshes and carry away waste, began as an open channel, and was covered over gradually; parts of it still carry rainwater in central Rome today.⁷ Rome's first aqueduct, a channel that carries water by gravity from a distant source, was the Aqua Appia, commissioned in 312 BC by the censor Appius Claudius Caecus.⁸

By the late 3rd century AD, 11 aqueducts served the city, with a combined length of about 780 to 800 km (485 to 500 miles).⁸ Only about 47 km (29 miles) of that ran above ground.⁸ The famous arches were the exception; most of the system was a buried, sloping channel.

Rome also produced one of the first infrastructure reports. Frontinus became the city's water commissioner (curator aquarum) in 97 AD and wrote De aquaeductu, an official account of the supply.⁸ Modern estimates based on his figures put the city's daily supply anywhere from about 520,000 to 635,000 cubic meters up to 1,000,000 cubic meters.⁸

The pattern these cities set has lasted ever since: bring clean water in by gravity, carry dirty water away by gravity, and lay out streets so both are possible.

Why were old cities so afraid of fire?

For roughly 1,500 years after Rome, most European cities drew water from wells, rivers and conduits, and human waste went into a cesspit, a pit beneath or beside a building where it collected until someone emptied it. In Tudor England, the people who did that work were called gong farmers. They were allowed to work only between 9 pm and 5 am, which is why they were also called "nightmen."⁹

The waste, known as night soil, was carted out of town.⁹ In London, much of it went to riverside wharves such as Dung Wharf and was shipped by barge to farms and market gardens.⁹ In effect, this was a recycling system. It began to come apart once flushing toilets sent waste into sewers and rivers instead of into pits.

Japan offers a non-European example. In the Edo period (1603-1868), local systems for circulating organic material formed between the early modern cities and the villages around them, and the use of night soil as fertilizer was especially common in the suburbs of Osaka and Edo (now Tokyo).¹⁰ Edo also organized against fire: the Kyōhō Reforms of 1720 created the machi bikeshi, town fire brigades made up of commoners appointed by town officials, which in time came to be seen as a competent force and helped samurai brigades fight the 1747 Edo Castle fire.¹¹

The bigger fear was fire. The Great Fire of London began on Sunday, September 2, 1666, in Thomas Farriner's bakery on Pudding Lane, and was mostly under control by September 5.¹² It destroyed 13,200 houses, 87 parish churches, St Paul's Cathedral, the Royal Exchange and the Guildhall, with damage estimated at £10 million.¹² (The recorded death toll is low and widely disputed, so we do not give a figure here.)

Two lasting city systems came out of the ashes. The first was organized firefighting: after the fire, insurance businesses hired men to fight fires, forming the first fire brigades.¹² The second was the building code, legal rules for how buildings must be built. The Rebuilding of London Act 1666, which received royal assent on February 8, 1667, favored brick and stone; regulated wall thickness, street widths and house heights; and banned jetties, the overhanging upper floors that let fire leap across narrow lanes.¹³ It was paid for with a duty on coal.¹³ Rebuilding under Christopher Wren's plans took more than 30 years, and the Monument to the fire, 202 feet (62 m) tall, went up in 1671-1677.¹²

Private insurers moved first, and governments followed with rules for everyone.

How did cholera build the modern sewer?

Industrial cities in the 1800s grew faster than their wells and cesspits could cope with. Cholera made the problem impossible to ignore. Britain's first cholera epidemic, which ran to 1832, killed about 30,000 people.¹⁴ The older explanation, miasma, held that disease spread through foul-smelling "bad air."

In 1854 a London doctor, John Snow, tested a different idea. An outbreak began in Soho on August 31, 1854, and about 500 people died within 10 days.¹⁴ Snow mapped where the victims lived and found the deaths clustered around a single public water pump on Broad Street.¹⁴ The pump's handle was removed, and a leaking sewer was later found to have contaminated the well.¹⁴ His theory that cholera spread through water was not accepted at first.¹⁴ Acceptance came after an 1866 outbreak in East London struck areas not yet connected to the city's new sewers.¹⁴

Those sewers had been prompted by smell rather than by Snow. In the hot summer of 1858, the Thames stank so badly that the episode became known as the "Great Stink."¹⁵ Joseph Bazalgette, chief engineer of the Metropolitan Board of Works, then built six intercepting sewers, large pipes that catch the flow of many smaller sewers before it reaches the river and carry it elsewhere.¹⁵ They totaled about 100 miles (160 km), fed by about 450 miles (725 km) of main sewers, and used 318 million bricks and Portland cement, with pumping stations at Abbey Mills, Deptford and Chelsea, among others.¹⁵ The work cost about £3 million at the time.¹⁵

The fix arrived before the science was settled. Bazalgette's sewers were designed partly to get rid of bad smells, and they cut cholera anyway, because they also kept sewage out of drinking water.

Paris rebuilt on an even larger scale. Napoleon III made Haussmann prefect of the Seine in 1853, with a mandate to "aerate, unify and beautify" the city; Haussmann was dismissed in January 1870.¹⁶ His program demolished 19,730 buildings containing about 120,000 homes and built 34,000 new buildings with about 215,300 apartments.¹⁶ Paris had 142 km (88 miles) of sewers in 1852, and the network grew about fourfold by 1869, while the engineer Eugène Belgrand's new aqueducts nearly doubled the water available per person.¹⁶ The program also created four major parks and 24 new squares.¹⁶

Historians still argue about it: critics have said the wide new boulevards were meant partly to make uprisings easier to put down, and defenders call that a secondary motive. How much rents rose and how many working Parisians were pushed out are also disputed.

Chicago had a different problem: it was too flat to drain. Ellis Chesbrough left Boston in 1855 to become engineer of Chicago's Board of Sewerage Commissioners, at a time when Chicago had the highest death rate of any US city.¹⁷ Because the ground was too low for sewers to flow, he had downtown raised about 10 feet (3 m), with buildings lifted on jackscrews.¹⁷ He also built a water tunnel two miles (3.2 km) out under Lake Michigan to an offshore intake, called a crib.¹⁷

In January 1900, gates at Lockport opened on the 28-mile (45 km) Sanitary and Ship Canal, and the Chicago River reversed direction, carrying sewage away from the lake.¹⁸ Chicago did not build sewage treatment plants until the 1920s.¹⁸ (One widely repeated story, that disease killed about 12 percent of Chicagoans in 1885, is a documented myth: mortality records show no cholera deaths that year, and the Chicago Tribune retracted the claim in 2005.¹⁹)

In London and Chicago alike, the first solution was to move waste somewhere else: farther down the Thames, or down the Illinois River. Treating it came decades later.

In Boston: making land and fighting fire

Boston's version of the sanitary story starts with a dam. A milldam closing off the tidal Back Bay was chartered in 1814; it cut off the tide's daily flushing and left a stagnant, polluted basin behind it.²⁰ Boston's answer was to fill the bay in. Filling began in 1857, and Back Bay itself was filled by 1882, with the work reaching Kenmore Square by 1890 and the Fens by 1900.²⁰ The gravel came by rail from Needham, about 9 miles (14.5 km) away, with a 35-car train arriving every 45 minutes, day and night.²⁰

The neighborhood sits on landfill, ground made by dumping earth and gravel into marsh and tidal flats. That is one reason flooding is a live question in Boston today (more in How cities are adapting to a changing climate).

Boston was also first with a new kind of network. On April 28, 1852, the city put into service an electric fire alarm telegraph, a system of street boxes wired to a central office so that pulling a box reported a fire's location at once.¹ William F. Channing invented it with help from Moses G. Farmer, and it started with 40 boxes.¹ The first alarm came in at 8:25 pm the next day.¹

Twenty years later, the network did not stop the city's worst fire. The Great Boston Fire began at 7:20 pm on November 9, 1872, at 83-87 Summer Street, and was contained around midday on November 10.²¹

It burned about 65 acres (26 hectares) and destroyed 776 buildings; reported deaths range from 26 to at least 30, and losses totaled $73.5 million at the time.²¹ The causes were a list of infrastructure failures: wooden mansard roofs, weak water pressure, too few hydrants with mismatched hose couplings, and alarm boxes that were kept locked.²¹ An outbreak of equine flu among the fire department's horses is often blamed, but a city commission found it caused only a few minutes' delay.²¹ Afterward, Boston widened streets, created Post Office Square and adopted limits on building height and area.²¹

In our reading, 1872 is the clearest early case in this guide of something that keeps coming back: the technology existed, and the way it was run held it back. A locked alarm box is a management decision, not an engineering one.

When did cities get gas, electricity and subways?

From the early 1800s to 1900, cities added a new layer of network roughly every decade, each with its own company, its own franchise and its own pipes, wires or tracks under the street.

• Gas light, London, 1807-1820s. In 1807, Frederick Winsor lit lamps on Pall Mall, using old musket barrels as gas pipes.²² The Gas Light and Coke Company, the world's first gas company, received a royal charter in 1812, and gas lit Westminster Bridge in 1813.²² By the 1820s, London had about 50,000 gas lamps on about 300 miles (480 km) of pipe.²²
• Underground railway, London, 1863. The Metropolitan Railway opened with 3.5 miles (5.6 km) of line between Paddington and Farringdon in January 1863.²³ Sources disagree slightly on the day: the National Lottery Heritage Fund gives January 9,²³ while many Underground histories treat January 9 as the ceremonial opening and give January 10 for the first public service.
• Telephone, 1876. Alexander Graham Bell's telephone patent was issued on March 7, 1876, and his notebook for March 10 records the words "Mr. Watson - Come here - I want to see you."²⁴
• Central power station, New York, 1882. Thomas Edison's Pearl Street Station began supplying customers on September 4, 1882.²⁵ On the first day it served about 85 customers and about 400 lamps; within a year it had 513 customers and about 10,000 lamps.²⁵ It ran on low-voltage direct current from six coal-fired dynamos and covered about a quarter of a square mile (0.65 square km) of lower Manhattan.²⁵ It was a central station: one plant serving many buildings over a network of wires, instead of each building making its own power.
• Electric streetcars, Richmond, 1888. Frank Sprague's Richmond Union Passenger Railway in Virginia began running in February 1888 and became the model for electric street railways.²⁶ By 1895 the US had almost 900 electric street railways on about 11,000 miles (17,700 km) of track, and horse-drawn street railways had nearly disappeared.²⁶

At the same time, two inventions let cities grow upward. The first passenger elevator was installed in 1857 in the Haughwout store in New York City, and elevators made buildings taller than four or five stories practical.²⁷

Then came the steel frame, a grid of metal columns and beams that carries a building's weight so the outer walls no longer have to. The Home Insurance Building in Chicago, designed by William Le Baron Jenney and completed in 1885, had 10 stories (later 12), and its frame combined wrought iron, cast iron and Bessemer steel beams; it was demolished in 1931.²⁸ PBS calls it the first tall building held up by a steel skeleton,²⁷ and it is often called the first skyscraper, though that title is debated, partly because its frame was mixed iron and steel.

The 1880s and 1890s pulled cities in two directions at once. Streetcars let people live farther out along the lines, in what became known as streetcar suburbs, while elevators and steel let downtowns stack higher. Both trends depended on the new networks, and both made the street overhead and the ground underneath more crowded.

In Boston: the first American subway and a reservoir

Richmond's streetcars had a direct effect on Boston: their success helped persuade the city to approve a large electrification project.²⁶ Electric cars soon clogged downtown, and Boston went underground. Construction of the Tremont Street Subway began on March 28, 1895, and it opened at 6 am on September 1, 1897, running from Park Street to Boylston, as the first subway in the United States.² More than 100,000 people rode it on the first day.² It was built to relieve streetcar congestion and modeled on lines in London, Glasgow and Budapest; the legislature appropriated $5 million, and the project came in early and under budget.²

Boston was also where the telephone first worked. On March 10, 1876, Alexander Graham Bell spoke the first intelligible words over an electric wire - "Mr. Watson, come here! I want to see you" - in the attic laboratory he shared with Thomas Watson at 5 Exeter Place in Boston.²⁹ An IEEE Milestone plaque now stands near Lafayette Place, at Avenue de Lafayette and Essex Street, and a separate marker at 109 Court Street marks the original laboratory where the two built their telephone equipment.²⁹

The networked era's biggest Boston project was water, and its cost fell on people far from the city. To build the Quabbin Reservoir in central Massachusetts, the state discontinued the towns of Dana, Enfield, Greenwich and Prescott on April 28, 1938.³⁰ About 2,500 residents left, and 7,613 graves were moved.³⁰ Flooding began in July 1939, and the reservoir was declared full on June 22, 1946.³⁰

It holds 412 billion gallons (about 1.56 trillion liters) on 80,443 acres (about 32,550 hectares) taken by eminent domain, the government's power to take private property for public use with payment, and it supplies 46 metro Boston communities.³⁰ Greater Boston's tap water still depends on a sacrifice made by people who never lived in the city (the system today is covered in Where your tap water comes from).

How did the car remake the city?

In the middle of the 20th century, governments in many countries rebuilt cities around the car. The US version was the largest. The Federal-Aid Highway Act of 1956 authorized "over 41,000 miles" (66,000 km) of interstate highways,³¹ and the federal government offered to pay 90% of the cost.³² With that much money on the table, states had strong reasons to build, and many urban routes were run through the neighborhoods that were cheapest to clear and had the least political power to resist.

In Atlanta, I-75, I-85 and I-20 destroyed downtown street grids and divided neighborhoods, and the areas cleared were mostly low-income Black communities.³¹ Overtown in Miami had an estimated 40,000 residents before I-95; about 8,000 remained after construction.³² Rondo in St. Paul, Minnesota, lost an estimated 600 family homes and 300 businesses to I-94.³² Syracuse's 15th Ward (I-81) and the neighborhoods along New York's Cross-Bronx Expressway are other often-cited cases.³² Across the whole program, the US Department of Transportation has estimated that more than 475,000 households, and over a million people, were displaced by federal highway construction.³² (That figure comes to us secondhand, through HISTORY.com; we could not locate the original DOT document.)

The same legal tools, eminent domain and federal money, were also used to clear areas labeled as slums under urban renewal programs. The two efforts often worked together, and in many cities it is hard to separate the damage done by one from the other.

The program's defenders and its critics are often describing the same roads, which sped travel between cities and suburbs for some people and demolished the homes of others.

Boston also had its own fight over new highways. The planned Inner Belt (I-695) was to be an eight-lane, mostly elevated loop of about 10 miles through Charlestown, Somerville, Cambridge, Brookline, the Fenway, Roxbury and the South End, and the eight-lane Southwest Expressway would have cost Roxbury 5,000 homes.³³

Residents, a coalition called the Greater Boston Committee on the Transportation Crisis, and groups including the Black Panther Party and the Black United Front in Roxbury organized against them.³³ On February 11, 1970, Governor Francis Sargent froze new construction and land-taking for a restudy, and on November 30, 1972, he cancelled both roads; Massachusetts then became the first state to put highway funds toward transit, including the Red Line extension to Alewife and the Orange Line relocation.³³

Boston's best-known highway story comes at the end of the century, when the city tried to undo part of the car era. The Central Artery/Tunnel Project, known as the Big Dig, replaced the elevated Central Artery (I-93) through downtown with tunnels.³⁴ It was conceived in the 1970s, begun in 1991 and completed in 2007, and Britannica calls it the largest and most expensive highway project in US history.³⁵ The Zakim Bridge was completed in 2003.³⁵ The cost depends on what you count:

In July 2006, a tunnel ceiling collapse killed a motorist and led to a $26 million settlement.³⁴ The project also freed about 300 acres (120 hectares) of land and turned the old highway corridor into the Rose Kennedy Greenway park.³⁴

Why did cities start cleaning up?

After about 1970, the main job in many wealthy countries shifted from building new networks to cleaning up and protecting the ones already there. In the US, the shift had a famous image. Ohio's Cuyahoga River burned at least nine times between 1868 and 1952.³⁶ A fire on June 22, 1969, helped build the movement behind the first Earth Day in 1970 and the founding of the US Environmental Protection Agency in December 1970.³⁶

The legal tool that followed was water law. The 1948 Federal Water Pollution Control Act was the first major US water pollution law, and its 1972 amendments, which became known as the Clean Water Act, required permits for point-source discharges, meaning pollution from a single identifiable outlet such as a pipe, and funded grants to build sewage treatment plants.³⁷ Congress passed it over President Nixon's veto.³⁶ In 1987, Congress replaced the construction grants with the Clean Water State Revolving Fund.³⁷ That move away from direct federal grants still shapes how US cities pay for water and sewer work, a subject covered in Who pays for the city.

In Boston, the law arrived through the courts. In the 1980s, combined sewer overflows, outlets where pipes carrying both sewage and rainwater spill into waterways when they fill up, sent about 3.3 billion gallons (12.5 billion liters) a year into Boston Harbor.³ The Massachusetts Water Resources Authority (MWRA) took over Greater Boston's water and sewer systems in 1985, and in 1986 federal Judge A. David Mazzone set a 13-year court-ordered construction schedule, which he oversaw until 2004.³

Dumping of sewage sludge into the harbor ended in 1991, and new primary treatment (letting solids settle out) began at Deer Island in 1995.³ Secondary treatment, which uses bacteria to break down dissolved pollution, started up in stages from 1997, and all of it was running in 2001-2005.³ Since 2000, treated effluent has traveled through a tunnel to an outfall 9.5 miles (15 km) out in Massachusetts Bay instead of into the harbor.³

The cleanup did not come from voluntary investment. It came from a lawsuit, a judge and a schedule. And as with the river fire, the harbor and the Great Stink, the action came after a visible failure.

What's changing now (2026): data and climate

The 2010s brought a new promise: the smart city, using sensors, data and software to run traffic, energy, water and other services. Some cities have folded these tools into everyday operations, and some projects ran into public resistance.

Much of this is now routine. Water and wastewater utilities run SCADA (supervisory control and data acquisition) systems that send sensor readings in real time and let a central control station monitor remote pump stations and the distribution network over a wide-area network.³⁸ In Boston, as of 2026, the 311 service center takes non-emergency requests by phone, online and through the BOS:311 app 24 hours a day, every day of the year, for problems from potholes and street lights to missed trash pickups.³⁹

The best-known case of resistance is Toronto. Sidewalk Labs, owned by Google's parent company Alphabet, proposed a waterfront district there called Quayside. Waterfront Toronto, the public agency in charge, limited the plan to 12 acres (5 hectares) from the roughly 190 acres (77 hectares) Sidewalk had proposed, and residents and advocates objected to its plans for collecting data.⁴⁰ Sidewalk Labs cancelled the project in May 2020, citing COVID-19 and economic uncertainty.⁴⁰ Supporters saw a chance to test new technology at scale; critics saw too much private control over public data.

Climate is now part of the job description of city government. London's Thames Barrier, a storm surge barrier of movable gates across the river, became operational in 1982, and as of November 17, 2025, it had closed 221 times for flood defense.⁴¹ Its operator's Thames Estuary 2100 plan sets out how flood risk will be managed to the end of the century and adjusts as sea-level projections change.⁴¹

In Boston, the city published Climate Ready Boston in December 2016.⁴² It projected rising relative sea levels even with sharp cuts in emissions, a growing risk of coastal flooding, and a possible tripling of heat-related deaths by 2050 without climate adaptation, meaning changes to infrastructure and planning that reduce the harm.⁴³ For a city that built Back Bay on filled marsh, the question of where the water goes is back where it started in 1814.

Each era added a layer to solve the problem of its day, and almost none of the older layers went away. A city in 2026 runs on all of them at once.

How this guide is organized

The rest of the guide takes those layers one at a time, starting with what comes into a building and ending with who pays for it. It begins with water, then power and light, then streets and signals, then transit, then waste, then emergencies and data. It closes with who runs it and pays for it: the agencies, authorities, workers and budgets behind every pipe and wire described here. Each chapter explains how its system works today, how it got that way, and what is changing now, with Boston as the running example.

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02A city is one machine

The short version: The rest of this guide takes a city apart one system at a time, but none of those systems runs alone. Electricity drives the pumps, signals, trains and phone networks; water from the mains is what fire crews fight with; one shared strip of street holds nearly every pipe and cable; and a single storm can hit all of it at once. When one system fails, the failure often travels into others, from the Great Boston Fire of 1872 to the 2018 Merrimack Valley gas explosions. This section maps those connections, so each chapter after it reads as one part of a single machine.

Why can't you understand one system at a time?

Each chapter in this guide follows one network, and usually one owner. In Boston, a commission created by state law runs the local water mains, sewers and storm drains,⁴⁴ a state authority supplies the water and treats the sewage,⁴⁵ Eversource runs the poles and wires,⁴⁶ and the city's Transportation Department runs most traffic signals from City Hall.⁴⁷

The networks ignore those boundaries. A city is a set of systems that lean on each other: water needs electricity, firefighting needs water, the subway needs electricity and pumps, and almost everything needs a phone or data line to be watched and dispatched. We call this interdependency, and it is the main reason this guide exists. A pothole, a power cut or a cloudburst rarely stays inside its own chapter.

Electricity runs almost everything else

More of the city depends on power than on anything else.

• Water and sewage. Eversource's restoration order puts water and sewage plants among the "critical facilities" restored right after life-threatening calls and blocked roads, alongside hospitals and fire stations.⁴⁸ Sewers have needed pumps from the start: Bazalgette's London system of the 1860s had pumping stations at Abbey Mills, Deptford and Chelsea.¹⁵
• Tall buildings. Newer New York buildings increasingly pump water up from the basement instead of using a rooftop tank.⁴⁹ A gravity tank keeps flowing through a blackout until it runs dry, while a pump without backup power stops when the power does (more in Why water reaches the 40th floor).
• Traffic signals. Load switches in each cabinet turn the controller's 12-volt logic into the 120-volt AC that lights the lamps.⁵⁰
• Transit. Boston's subway lines run on 600 volts DC from 48 traction power substations, and the same network powers tunnel lighting and ventilation fans.⁵¹ New York's subway has 300 pump rooms that remove about 13 million gallons of water on a normal day.⁵²
• Telecom. Phone, cable and fiber lines hang on the same poles as the power lines,⁵³ and 5G small cells are mounted on streetlights.⁵⁴
• Heat. As of late 2025, Boston's district steam came partly from a 42-megawatt electric boiler,⁵⁵ and ISO New England expects winter peak demand to grow about 2.9% a year through 2035 as buildings switch to electric heat.⁵⁶

Phones need power too. In the US, the Federal Communications Commission (FCC) adopted a rule requiring at least 24 hours of backup power for equipment inside telephone central offices and eight hours for cell sites and remote switches,⁵⁷ but the White House Office of Management and Budget rejected it as too burdensome in 2008, and the FCC did not contest the decision, so the rule did not take effect.⁵⁸ In the August 2003 Northeast blackout, backup generators at some cell sites ran out of fuel, and Verizon's emergency generators failed several times, taking 911 out of service for about 15 minutes at a time.⁵⁹

The flow also runs the other way: Boston burns most of its residential trash at waste-to-energy plants,⁶⁰ and Copenhagen's CopenHill plant supplies power and heat for 150,000 homes.⁶¹

Water is the fire department's supply

A serious fire is fought with water from the city's mains. The Great Boston Fire of 1872 is the early lesson: the causes on record include weak water pressure and too few hydrants, with hose couplings that did not match.²¹

Each hydrant hangs off the street main on its own pipe, called the hydrant branch or lateral, with a valve that lets the water utility shut off that hydrant alone.⁶² The US Fire Administration's 2008 guide puts the minimum water need of most homes at 500 gallons per minute (about 1,900 liters per minute), while commercial properties can need up to 12,000 gallons per minute for four hours.⁶³ In Boston, the Boston Water and Sewer Commission runs fire flow tests at hydrants for engineers, developers and sprinkler designers, charging $660 per test as of 2026.⁶⁴

Tall buildings carry the link indoors. A standpipe feeds hose valves on each floor, and fire engines pump water into it through a Siamese connection on the outside wall.⁶⁵ In New York's rooftop tanks, the bottom of the tank is reserved for emergencies.⁶⁶

So a water main failure is also a firefighting problem. In May 2010, a main break showed that the tunnels carrying about 60% of metro Boston's daily water had no backup, which is why the Massachusetts Water Resources Authority (MWRA) is building two new deep tunnels.⁶⁷ Redundancy in the water system is also fire protection.

The street is a shared corridor

Under a Boston block can sit a water main and a sewer belonging to the Boston Water and Sewer Commission, which runs about 1,015 miles (1,630 km) of water main and 1,435 miles (2,310 km) of sewer and storm drain.⁴⁴ Gas, electric, telecom and, downtown, steam lines share the ground, each owned by someone else.

Every owner digs, and every dig risks someone else's line. In Massachusetts, anyone excavating must premark the area in white, then notify Dig Safe, reachable at 811, at least 72 business hours ahead, so the utilities can come and mark their lines.⁶⁸ Cambridge bars digging in a street resurfaced within five years except in an emergency or with approval.⁶⁹ (See Roads, bridges, tunnels and the hole in your street.)

The worst Massachusetts case of one buried job disturbing another came during work meant to improve safety. On September 13, 2018, a Columbia Gas crew replacing a cast-iron main abandoned the old pipe while the sensing lines for the area's pressure regulators were still attached.⁷⁰ The regulators read falling pressure and opened fully, sending high-pressure gas into homes.⁷¹ Fires and explosions damaged 131 structures, one person was killed, and 10,894 customers lost gas.⁷⁰ In our reading, it was at root a records failure, a matter of knowing what is connected to what.

What's under one downtown street?

A walk from the sidewalk down. The order and depth of the buried layers is our explanation; real streets vary, and only the owners' maps show what is where.

• On the sidewalk. A streetlight, one of about 71,000 the city owns,⁷² perhaps carrying a small cell.⁵⁴ A red fire alarm box, one of about 1,250.⁷³ A signal cabinet holding the controller.⁷⁴ A Siamese connection on a building wall.⁶⁵ Perhaps white paint and colored marks from a Dig Safe ticket.⁶⁸
• The pavement. A surface layer on crushed rock on native soil, the subgrade.⁷⁵
• Below the pavement. Mostly wire. Boston's streetlights alone use about 4 million feet of conduit and 32,000 pull boxes.⁷⁶ Downtown power runs through underground networks,⁴⁶ with transformers in vaults and a network protector that opens if power flows backward into a dead feeder.⁷⁷ The fire alarm boxes run on their own circuits, independent of the telephone and electric lines.⁷⁸
• Pipes. Gas (Massachusetts still had 4,049 miles of leak-prone cast-iron and bare-steel gas pipe in 2025),⁷⁹ district steam (about 25 miles of it in Boston and Cambridge),⁵⁵ water and sewer.⁴⁴ Sewers tend to sit lowest because they run downhill by gravity.
• Tunnels. Under parts of downtown, the subway. The 1897 Tremont Street tunnel was built cut-and-cover: a trench down the street, a box in it, a roof over it.⁸⁰
• Deep rock. MWRA's planned Northern and Southern water tunnels will run 200 to 450 feet (60 to 140 m) down.⁶⁷

Storms hit every system at once

• Rain. In combined sewers, heavy rain makes the pipes overflow untreated into rivers and harbors.⁸¹ New York's subway pumps remove about double their normal volume on a heavy-rain day.⁵²
• Wind and ice. Downed lines set off the restoration order: safety calls, blocked roads, critical facilities, the big lines, then single homes.⁴⁸
• Snow. Boston tows cars off main roads in a snow emergency so plows can work,⁸² and one season's update counted more than 74,862 tons of salt.⁸³ Salt then reaches the power system: 68% of Con Edison's 2014 manhole events came in January and February, when most road salt goes down.⁸⁴ Meltwater in cracked pavement freezes and leaves the voids that become spring potholes.⁷⁵
• Heat and sea. On June 24, 2025, New England's grid hit its highest peak in over a decade, with reserves short for more than three hours.⁸⁵ Climate Ready Boston found today's 1% annual-chance waterfront flood becoming a 10% chance after mid-century.⁴²

Data and telecom tie it together

Boston's Traffic Management Center had 699 of the city's almost 900 signals on its central system in 2020.⁴⁷ Columbia Gas's 2018 high-pressure alarms arrived at a monitoring center in Columbus, Ohio.⁸⁶ Eversource is installing smart meters and a distribution management system that show it where power is flowing.⁴⁶

Water and sewer utilities do the same with SCADA (supervisory control and data acquisition): sensors at pump stations and along the pipe network send readings in real time over a wide-area network to a primary control station, and controllers at treatment plants run the process automatically.³⁸ Those screens can be a target. In 2024, pro-Russia hacktivists reached internet-exposed control screens at water systems, pushed pumps and blowers past their normal limits, and locked operators out, forcing some utilities back to manual operation, according to the EPA and CISA.⁸⁷

The public sees the data layer too. Transit apps read GTFS schedules and live feeds, a real-time format the MBTA helped develop with Google.⁸⁸ 311 apps send a photo and GPS location to the city.⁸⁹ Networks swap internet traffic at the Boston Internet Exchange at One Summer Street.⁹⁰ (See 311, the wires under the street, and city data and From fire alarm boxes to 911.)

When one failure becomes several

• 1872, Boston. Locked alarm boxes, weak water pressure and mismatched hydrant couplings turned one fire into 776 burned buildings.²¹
• 2003, Northeast US and Ontario. On August 14, a blackout hit about 55 million people. In Cleveland, water service stopped when electric pumps lost power, and 4 million customers of Detroit's water system were told to boil water until August 18. In New York, more than 600 subway and commuter rail cars were trapped between stations; cell networks overloaded and some cell sites went dark when their power failed.⁵⁹
• 2005, New York. On the first day of a transit strike, NYC311 took a record 240,000 calls.⁹¹
• June 2024, Boston. During a 911 outage, the police commissioner told residents to use the street fire alarm boxes.⁷³
• December 2024, Boston. The day the MBTA cleared its last slow zone, a cracked rail near Wollaston put riders on shuttle buses; the governor said slow zones had cost "nearly a million dollars every day in GDP."⁹²
• Any day. A signal that loses its link to the control room keeps running, "out of sync with the rest of the signals in that corridor."⁴⁷

In Boston

Follow a glass of tap water: it leaves a state authority's tunnels, crosses into the commission's mains at one of 27 metered points,⁴⁴ and drains to MWRA's Deer Island plant.⁴⁵ Downtown, the power arrives underground⁴⁶ and the heat often as steam,⁹⁷ while the alarm boxes keep a wired network apart from the phone system.⁷⁸ Because the boxes do not share the phone network, they can still work when it fails; during the June 2024 911 outage, the police commissioner told residents to use them.⁷³

How it changed

Nobody planned the connections as a whole. Cities added a network roughly every decade: gas light in London from 1807, Edison's central power station in 1882, electric streetcars in Richmond in 1888.²²²⁵²⁶ One layer created the next. Richmond helped persuade Boston to electrify,²⁶ electric cars clogged downtown, and Boston dug the first US subway in 1897.² Each network went into the same streets as the last.

What's changing now (2026)

• More runs on the grid. Heat pumps push winter peaks up,⁵⁶ Boston's steam system is adding electric boilers and a river heat pump,⁵⁵ and regulators are asking whether every old gas main should be replaced.⁷⁹
• Signals that talk to cars. USDOT aims for vehicle-to-everything radios at 25% of signalized intersections in the 75 largest metros by 2028.⁹⁸
• 911 on internet protocol. In the US, FCC rules move emergency calls onto IP networks that carry text, photos and location.⁹⁹
• Shared flood risk. Many of the systems in the table share the same low-lying ground. Boston's planning watches low spots such as the land around Moakley Park and I-93, where water would enter and spread inland (see How cities are adapting to a changing climate).¹⁰⁰

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03Where your tap water comes from

The short version: City water starts as rain on a protected watershed or in a river, passes through a treatment plant, and travels through buried tunnels and mains to the tap, pushed by gravity, pumps or both. Pressure comes from height: every foot of water standing above a faucet adds about 0.433 psi.¹⁰¹ Greater Boston drinks from two forested reservoirs in central Massachusetts and is one of five major US systems with a waiver to skip filtration.¹⁰²¹⁰³ The weak points are the pipes themselves: tunnels with no backup, and lead service lines that a federal rule, now being challenged in court, requires most US utilities to replace by the end of 2037.⁶⁷¹⁰⁴

Where does city water come from?

Every piped water supply is a chain of four links: a source (a reservoir, river, lake or aquifer), treatment, a distribution network of mains and service pipes, and storage that keeps pressure steady when demand swings. A failure in any one link reaches the tap.

The source is usually defined by its watershed: the land that drains rain and snowmelt into a particular river or reservoir. A utility that owns or controls a clean watershed starts with cleaner water, and some of the oldest big-city systems were built around that idea.

Greater Boston's supply is a clear example. The Quabbin Reservoir holds 412 billion gallons (about 1.56 billion cubic meters) and the Wachusett Reservoir holds 65 billion gallons, for 477 billion gallons of combined source storage.¹⁰² More than 85% of the land in the two watersheds is forest and wetland, and the watersheds are tested and patrolled.¹⁰⁵ Two older reservoirs, the Sudbury Reservoir and Framingham Reservoir #3, are kept as backup and hold another 7.7 billion gallons.¹⁰²

New York City works on a similar plan at a larger scale. Its Catskill and Delaware supplies come from six reservoirs west of the Hudson River and serve more than 9.5 million people.¹⁰³

The number that matters most for a reservoir system is safe yield: how much water the supply can deliver every day, reliably, through a long drought. For the Massachusetts Water Resources Authority (MWRA), which runs Greater Boston's wholesale system, safe yield is about 300 million gallons per day (mgd), or about 1.1 million cubic meters.¹⁰² Average demand was 194.3 mgd in 2023 and 201.2 mgd in 2024 (a preliminary figure).¹⁰²

Why do some big cities skip filtration?

Most surface-water systems run their water through a sequence of chemical and physical steps that clump fine particles together, let them settle, and filter what is left.

Concord, New Hampshire, which draws from Penacook Lake, describes a typical sequence. A coagulant is added to make particles stick together into floc; the water is mixed fast, then gently, so the floc grows (flocculation); it slows in a sedimentation basin so the heavy clusters settle and are scraped away; and it then passes down through a 3-foot filter of silica sand and granular activated carbon.¹⁰⁶ Chlorine and then chloramine are added afterward for disinfection.¹⁰⁶

A few cities with exceptionally protected sources are legally allowed to skip the filter. The Natural Resources Defense Council (NRDC) counts five major US systems with these filtration waivers: New York, Seattle, Portland (Oregon), San Francisco and Boston.¹⁰³ New York's current waiver was issued by the New York State Health Department in December 2017 and is scheduled to last until 2027.¹⁰³

In our reading, "filtration avoidance" is a regulatory status, not a loophole. A utility keeps it by keeping its watershed clean, through land purchases, patrols and limits on development, and by proving it with water testing.

Boston's waiver was fought over in court. On February 12, 1998, the US government sued MWRA and the Metropolitan District Commission to require filtration under the Safe Drinking Water Act.¹⁰⁷ On May 5, 2000, the federal district court declined to order filtration and accepted MWRA's ozone-based plan instead; the court put the cost of a filtration plant at about $180 million.¹⁰⁷ The First Circuit Court of Appeals affirmed that ruling on July 16, 2001.¹⁰⁷ The idea was not new: when the Quabbin was built, it was described as a pure upland supply, delivered by gravity, that would "not require filtration."¹⁰⁸

What actually happens at the treatment plant?

Since July 2005, metro Boston's water has been treated at the John J. Carroll Water Treatment Plant in Marlborough.¹⁰⁵ It was designed for an average of 275 mgd and a peak of 405 mgd.¹⁰⁵ The steps, in order:¹⁰⁵

The last step is easy to overlook and arguably matters most to anyone living in an old building. Corrosion control means tuning the water's chemistry so it does not eat the metal it travels through.¹⁰⁵

Fluoridation is a policy decision as much as a treatment step, and it has become contested in parts of the US.

In 2025, Utah (HB 81, enacted in March) and Florida (SB 700, signed by Governor Ron DeSantis in May) passed laws barring local water systems from adding fluoride.¹⁰⁹ In April 2025, Kennedy said he would tell CDC to stop recommending community water fluoridation and would assemble a task force to study the issue; as the Associated Press noted, states and localities make their own fluoridation decisions.¹¹⁰ The same month, EPA said it would review new scientific information on fluoride to inform a possible revision of its drinking water limit, now a maximum contaminant level of 4.0 mg/L.¹¹¹ A Congressional Research Service report dated May 16, 2025 found no official HHS statement on the change yet, and said the Community Preventive Services Task Force's 2013 recommendation remained its most current.¹¹¹ On May 13, 2025, HHS announced that FDA was moving to remove concentrated ingestible fluoride prescription products for children from the market; HHS Secretary Robert F. Kennedy Jr. called ending ingestible fluoride "long overdue."¹¹² CDC's published recommendation, last reviewed in May 2024, remains community water fluoridation at 0.7 mg/L, the level the US Public Health Service set to balance benefits against potential harms.¹¹³

How does water get from the reservoir to your faucet?

Much of the work is done by gravity. MWRA's Quabbin Tunnel runs in both directions: in high-water months it carries surplus Ware River flow west into the Quabbin, and at other times it carries water east.¹⁰⁸ Its eastern section, the Wachusett-Colebrook Tunnel, was begun in 1926.¹⁰⁸

Closer to the city, the MetroWest Water Supply Tunnel runs 17.6 miles (28 km) from Marlborough to Weston, parallel to the Massachusetts Turnpike.¹¹⁴ It was mined 16 feet (4.9 m) across, finished at 14 feet, and lies 200 to 500 feet (60 to 150 m) underground.¹¹⁴ It went into service in November 2003 at an estimated $665 million, under its 1995 budget of $728 million, and it was built to back up a single aqueduct from the 1940s, the Hultman.¹¹⁴ Inside the metro area, the City Tunnel, City Tunnel Extension and Dorchester Tunnel carry about 60% of daily demand.⁶⁷ MWRA also keeps 282.7 million gallons in covered distribution storage.¹⁰²

From the tunnels, water moves into local mains run by each city or town, then through a service line, the pipe that connects a building to the main under the street.

Pressure follows from height. Each foot of water standing above a point adds about 0.433 pounds per square inch (psi) of pressure there, or roughly 9.8 kilopascals per meter.¹⁰¹ Our arithmetic: a water surface 100 feet (30 m) above a faucet delivers about 43 psi before friction losses; 200 feet delivers about 87 psi. That is why reservoirs sit on high ground, why gravity systems were the first choice for 19th- and early 20th-century engineers, and why pumping is needed wherever the source is too low (or the faucet too high; see Why water reaches the 40th floor).

Why are water towers so high?

The same arithmetic explains the water tower. A tower or standpipe is a reservoir lifted into the air: the height of its water surface sets the pressure in the mains around it. Utilities can pump water up when demand is low and let it flow down when everyone showers at once, and the stored water is there for firefighting.

A 2001 technical brief from the National Drinking Water Clearinghouse at West Virginia University lists the same roles: storage lets a utility pump at the average rather than the peak rate, holds a reserve for firefighting and other emergencies, and keeps pressure uniform.¹¹⁵ Tanks are drawn down during peak hours and refilled when demand is lowest, late at night and early in the morning.¹¹⁵ The brief gives minimum acceptable system pressures of 35 to 40 psi, with maximums generally 100 to 120 psi.¹¹⁵

Why do water mains break?

Pipes age, the ground shifts and freezes, and sudden pressure changes stress joints. When a small main breaks, a street floods and a few blocks lose water. When a trunk line fails, a whole region can lose it.

Greater Boston learned this in May 2010, when a water main break made clear that the tunnels carrying 60% of metro demand had no backup.⁶⁷ MWRA's response is the Metropolitan Water Tunnel Program, which adds about 15 miles (24 km) of deep rock tunnel: a 4.8-mile Northern Tunnel and a 10-mile Southern Tunnel, each 10 to 12 feet across and 200 to 450 feet deep.⁶⁷ The estimated cost is $2.1 billion (in MWRA's proposed FY25 capital plan), with construction planned for about 2027 to 2040.⁶⁷

Redundancy is the recurring theme of modern water engineering in old cities. The MetroWest tunnel backed up a single aqueduct; the new tunnels back up the city tunnels. A system with one path is one bad coupling away from a regional emergency.

How often do mains break nationally? A Utah State University study of 802 utilities in the US and Canada, dated December 2023, found 11.1 breaks per 100 miles of pipe per year, down about 20% from 14.0 in its 2018 study; cast iron failed most often, at 28.6 breaks per 100 miles.¹¹⁶ Utilities also hunt for leaks before they become breaks. Leaking water makes the pipe vibrate, and crews listen at valves and hydrants or through the ground with sensors and microphones; a correlator times when the sound reaches two sensors on either side of a suspected leak to estimate where it is.¹¹⁷

Are there still lead pipes, and who has to replace them?

Yes. EPA estimates that "up to 9 million homes" in the US are still served by them.¹¹⁸ Treatment plants adjust water chemistry to reduce how much lead and copper leaches out of old plumbing, which is the corrosion control step described above.¹⁰⁵

Flint, Michigan, shows what happens when that step is skipped. On April 25, 2014, the city switched from the Detroit system to the Flint River to save money, and it did not add the anti-corrosion treatment that builds a protective scale inside old pipes, so lead leached into the water.¹¹⁹ Flint was switched back to Detroit water in October 2015.¹¹⁹

On October 8, 2024, EPA announced the Lead and Copper Rule Improvements (LCRI).¹¹⁸ Its main terms, as of October 2026:

• Most US water systems must replace lead service lines, and lines of unknown material, within 10 years; systems with a high share of lead lines may get more time.¹¹⁸
• The action level, the lead concentration that triggers required steps by a utility, drops from 15 to 10 micrograms per liter (parts per billion).¹¹⁸
• The baseline inventory and replacement plan are due November 1, 2027, when mandatory replacement begins.¹⁰⁴
• The required average replacement rate of 10% a year is measured from December 31, 2030, and replacement must be complete by December 31, 2037.¹⁰⁴
• Partial replacements, where only the utility's section of a line is swapped, are banned from November 1, 2027, except during emergency repairs.¹⁰⁴
• The Bipartisan Infrastructure Law provided $15 billion over five years for lead line work.¹¹⁸

The rule is being challenged in court; see "What's changing now" below.

In Boston

Greater Boston's water system is a two-level arrangement. MWRA is the wholesaler: it owns the reservoirs, tunnels and treatment plant and sells water to cities and towns, which run their own local pipes. MWRA describes its reach two ways on the same web page, as "2.5 million people in 53 communities" and as "over 3.1 million customers in 61 communities."⁶⁷

The system is notable for using less water than it did a generation ago. Withdrawals ran above safe yield in the 1980s, and after MWRA started a conservation program in 1986, they dropped below safe yield by 1989.¹⁰² Demand was about 200 mgd in 2024, well under the Carroll plant's 275 mgd design average.¹⁰⁵

Dry years still register. MWRA has listed the Quabbin in "Below Normal" drought status since February 2026, and it remained there as of June 1, 2026.¹⁰² With 477 billion gallons in storage and demand around 200 mgd, our arithmetic says the reservoirs hold several years of supply, which is why a "Below Normal" listing is a watch status rather than an emergency.

On lead, MWRA's corrosion control is the regional defense.¹⁰⁵ Replacing the pipes themselves is up to the local water departments.

In Boston, the Boston Water and Sewer Commission (BWSC) replaces the private section of a lead service line, from the property line into the building, "at no cost to the owner" for eligible properties.¹²⁰ It began covering that cost in August 2023, using federal Bipartisan Infrastructure Law money.¹²¹ As of March 2024, BWSC had identified roughly 3,000 lead lines, said there might be thousands more, and only about 400 owners had used the free program.¹²² We did not find a BWSC target date for finishing.

How it changed

US city water started with gravity. New York's Croton Aqueduct, opened in 1842, fed reservoirs that sat about 60 feet above the city.⁴⁹

Boston built its supply westward in stages. Work on the Wachusett-Colebrook Tunnel began in 1926.¹⁰⁸ Construction of the Quabbin began in 1936, by damming the Swift River.¹⁰⁸ To make room for it, the towns of Dana, Enfield, Greenwich and Prescott were disincorporated at midnight on April 28, 1938, under legislation passed in 1927.¹²³ About 2,500 residents were displaced, and about 7,600 graves were moved to Quabbin Park Cemetery in Ware.¹²³

Filling began on August 14, 1939, by MWRA's account (Mass Humanities says July 1939³⁰), and finished in 1946, when water first flowed over the spillway; at completion it was described as "the largest man-made reservoir in the world devoted solely to water supply."¹⁰⁸ (The longer story of how cities came to build systems like this is in How cities came to need infrastructure.)

The late 20th century brought regulation and conservation. MWRA took over Greater Boston's water and sewer systems in 1985.¹²⁴ Its conservation program began in 1986.¹⁰² The filtration lawsuit ran from 1998 to 2001, and the Carroll plant opened in 2005, with UV added in 2014.¹⁰⁷¹⁰⁵ The MetroWest tunnel followed in 2003, and the 2010 break started the next round of tunnel building.¹¹⁴⁶⁷

What's changing now (2026)

• The lead rule is in court. Water utilities led by the American Water Works Association (AWWA) have challenged the LCRI in the D.C. Circuit.¹²⁵ NRDC intervened on December 20, 2024; final briefs, including EPA's defense of the rule, were filed April 17, 2026; and oral argument was held September 30, 2026.¹²⁵ A decision is expected about 6 to 12 months after argument.¹²⁵ A Tennessee state guide to the rule, published in May 2026, notes that its guidance "may change pending EPA rule updates."¹⁰⁴
• New York's waiver runs to 2027. The current filtration waiver for the Catskill and Delaware supplies is scheduled to last until 2027, so a renewal decision is approaching.¹⁰³
• Boston's backup tunnels are about to start. Construction of MWRA's Northern and Southern tunnels is planned to begin around 2027.⁶⁷
• Drought watch. The Quabbin has been in "Below Normal" drought status since February 2026.¹⁰²

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04Why water reaches the 40th floor

The short version: The pressure in a street main can push water up only a few stories. New York's first gravity aqueduct reached about the sixth floor, so taller buildings learned to pump water to a rooftop tank and let it fall back down.⁴⁹ Modern towers use booster pumps and split themselves into vertical pressure zones of about 9 to 10 floors, because the main US model plumbing code caps the pressure at a fixture at 80 psi.¹⁰¹¹²⁶ Fire protection runs on a separate set of pipes, the standpipes, which fire engines can feed from the street through a two-inlet fitting often called a Siamese connection.⁶⁵

How high can street pressure push water?

Water pressure and height are two ways of measuring the same thing. Each foot of water standing above a point adds about 0.433 pounds per square inch (psi) at that point, and with floors about 10 feet apart, each floor costs about 4.33 psi.¹⁰¹ To lift water one floor, you need about 4.33 psi of push; to deliver it at a usable pressure on that floor, you need more on top.

Plumbing engineers design for a minimum of about 35 psi at the highest fixture in a zone.¹⁰¹ Our arithmetic, using that figure: a street main at 60 psi could in theory lift water about 138 feet (42 m) before friction losses, but to arrive with 35 psi to spare, water can rise only about (60 - 35) / 0.433, or roughly 58 feet. That is five or six floors. Real buildings lose more pressure to pipe friction, meters and backflow preventers, and street pressure varies by neighborhood, so "five or six stories" is a rule of thumb rather than a constant.

History lines up with the arithmetic. New York's Croton Aqueduct, opened in 1842, was a gravity system whose reservoirs sat about 60 feet (18 m) above the city, which was enough to lift water to roughly the sixth story.⁴⁹

Why do New York buildings have wooden water tanks on the roof?

By the 1880s, New York buildings were rising above 10 stories, past what the Croton system could reach. The answer was a pump that lifted water to a tank on the roof, which then fed the floors below by gravity.⁴⁹ The city required rooftop tanks on buildings over six stories.⁴⁹

The tanks are still there, and many are still made of wood:

• A typical wooden tank is 10 to 12 feet (3 to 3.7 m) high, holds up to 10,000 gallons (about 38 cubic meters), and lasts 25 to 30 years.⁴⁹
• An electric pump refills the tank when the level drops, and the bottom of the tank is reserved for emergencies.⁶⁶
• Three family firms make about 90% of them: Rosenwach Tank Company, Isseks Brothers and American Pipe and Tank.⁴⁹⁶⁶ Isseks Brothers, founded in 1890, was the first firm formed specifically to make tanks.⁴⁹ Rosenwach builds with Western cedar.⁶⁶

How many tanks are there? Sources disagree: Vital City, in a 2026 piece by architectural historian Thomas Mellins, estimates more than 5,600, while the real estate site 6sqft says "up to 17,000."⁴⁹⁶⁶ The more recent figure is the lower one.

One reason the system has lasted: a gravity tank is simple, needs no power to deliver water, and keeps flowing during a blackout until it runs dry. The pump only has to run when the tank needs refilling.

What is a booster pump, and why are tanks disappearing?

A booster pump raises water pressure so it can reach upper floors. Newer New York buildings increasingly skip the roof tank and use pumps in the basement instead.⁴⁹ Large modern installations, such as the Burj Khalifa's, use booster sets with variable-speed drives.⁹³ A variable-speed pump speeds up and slows down to hold a steady pressure as demand changes, rather than filling a tank and shutting off.

The trade-off: a pumped system frees the roof, avoids the weight of a full tank, and keeps water from sitting in an open-air vessel, but it depends on power and controls. A tank system has the reverse profile.

What is a pressure zone?

Pumping water to the top of a tall building creates the opposite problem at the bottom: too much pressure. In the US, the International Plumbing Code (IPC), a model code, caps static pressure at fixtures at 80 psi (about 550 kPa) in section 604.8 and requires a pressure-reducing valve (PRV) wherever pressure would exceed that.¹²⁶

With a minimum of 35 psi at the top fixture and a maximum of 80 psi at the bottom, one zone can span only about 9 to 10 floors.¹⁰¹ Our arithmetic: (80 - 35) / 4.33 psi per floor is about 10 floors. So a tall building is plumbed as a stack of shorter buildings, each with its own pressure range, set by its height, its pumps and its valves.

The design choices that follow:¹⁰¹

• Separate booster pumps for each zone are the most efficient approach up to about 40 to 60 stories.
• Ultra-high-rises add intermediate tanks partway up. Pumps lift water to a tank on a mechanical floor, and a second set of pumps draws from that tank (a "suction tank") to feed the zones above.
• Water heaters are best placed inside the zone they serve, because PRVs complicate the loops that keep hot water circulating to distant fixtures.

This is one reason many towers have mechanical floors partway up, often with louvers instead of windows. Some of that space can house the pumps and tanks for the zones above.

How does the Burj Khalifa get water to the top?

The world's tallest building as of 2026, in Dubai, uses the staged approach at full scale. Xylem supplied six water transfer pump sets and seven pressure booster sets, all with variable-speed drives.⁹³ The pumps sit in the basement and on two technical floors about a third of the way up.⁹³ Average supply is 946,000 liters (about 250,000 gallons) a day, supplemented by water recovered from air-conditioning condensate, and about 1,000 cubic meters a day are boosted all the way to the top.⁹³

How do firefighters get water up a tall building?

Domestic plumbing and fire protection are separate systems with separate rules. A standpipe is a vertical pipe that feeds hose valves inside a larger building.⁶⁵ It lets firefighters connect hoses on the floor near the fire instead of dragging them up from the street.

On the outside of the building, at street level, is the fire department connection, often called a Siamese connection: a fitting with at least two inlets.⁶⁵ Fire engines pump water through the Siamese into the building's standpipes and sprinkler system to raise flow and pressure.⁶⁵ The US standard NFPA 14 requires a sign at each connection saying which system it feeds.⁶⁵

Pressure limits apply here too. NFPA 14 caps pressure at standpipe hose connections at 175 psi (about 1,200 kPa).¹²⁶ The same zoning logic that governs sinks and showers applies to fire hoses, at a higher ceiling, because hose crews need usable pressure without dangerous excess on the lower floors.

Standpipes come in two broad kinds. Wet standpipes keep water in the pipe at all times; automatic wet systems rely on a fire pump for pressure, while manual wet systems have no pump behind them.¹²⁷ Dry standpipes hold air instead, and in a manual dry system, with no pump or water supply of its own, firefighters must charge the pipe through the fire department connection before they can attack the fire.¹²⁷ The fire pumps themselves are covered in the US by a separate NFPA standard, NFPA 20, the Standard for the Installation of Stationary Pumps for Fire Protection.¹²⁸

In Boston

Greater Boston's regional supply arrives from the Quabbin and Wachusett reservoirs through deep gravity tunnels, and the local water departments distribute it from there.¹⁰⁸⁶⁷ (The full route is in Where your tap water comes from.) The physics in Boston is the same as in New York or Dubai: street pressure serves the lower floors, and anything tall pumps.

Our arithmetic, if a pressure cap like the IPC's 80 psi applies: a 40-story Boston tower would need about four pressure zones, and anything much taller would face the same choice New York and Dubai engineers face between per-zone boosters and intermediate tanks.¹⁰¹ The IPC is a model code, and Massachusetts writes its own.

Massachusetts does set its own cap at the same number. The state plumbing code, 248 CMR 10.14(2)(e), requires a pressure-reducing valve wherever pressure at a fixture exceeds 80 psi, and section 10.14(2)(d) requires a booster pump and pressure tank, or another compliant means, where supply pressure cannot meet the code's minimums.¹²⁹ On the street side, a 2013 BWSC planning presentation described Boston's distribution system as five pressure zones with pressures from 60 to 112 psi.¹³⁰ We did not find a source on whether rooftop tanks or basement boosters dominate in Boston's towers.

How it changed

• 1842: New York's Croton Aqueduct opens, delivering water by gravity to about the sixth story.⁴⁹
• 1880s: Buildings pass 10 stories, and pump-filled rooftop tanks become standard.⁴⁹
• 1890: Isseks Brothers is founded, the first company formed specifically to make New York's rooftop tanks.⁴⁹
• 20th century to now: Newer buildings increasingly use basement booster pumps instead of roof tanks.⁴⁹ Supertall towers stack pumps and tanks on intermediate floors, as the Burj Khalifa does.⁹³

In our reading, the history is a shift from storage to control. The roof tank stored water at the right height and let gravity do the work. Variable-speed pumps hold pressure electronically, floor by floor, and depend on power and controls to do it.

What's changing now (2026)

• New York's tanks are still being built. Writing in May 2026, Vital City describes wooden tanks as a living trade, with three family firms making most of them, even as newer buildings shift to basement pumps.⁴⁹
• Booster design keeps evolving. Engineering guidance published in November 2025 covers booster pump design for high-rises within the 80 psi fixture cap and 175 psi standpipe cap.¹²⁶
• Pumps run more of the system. As more towers use pumps instead of gravity tanks, backup power matters more for keeping water flowing to upper floors during an outage (see How electricity gets to your building).

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05Where it goes after you flush (or it rains)

The short version: In many older cities, toilets and storm drains empty into the same pipe, a combined sewer, and in heavy rain that pipe is designed to overflow untreated into the nearest river or harbor.⁸¹ EPA counts about 700 US communities with combined systems, and London, Chicago, Washington and Milwaukee have built deep storage tunnels to catch the overflow.^131132133 Boston went from a harbor a presidential candidate called a "harbor of shame" in 1988 to a sewage plant on Deer Island that is now a case study in recovery.¹³⁴¹²⁴ Cities increasingly pair the big pipes with green infrastructure that soaks up rain where it falls.¹³⁵

Where does sewage go after you flush?

The route is a branching tree run in reverse. A building's drain joins a lateral pipe under the sidewalk, the lateral joins a street sewer, street sewers join larger trunk sewers and interceptors, and the interceptors carry everything to a treatment plant. The treated water leaves through an outfall, the pipe or tunnel end where it is released into a river, lake or sea. Most of the trip runs downhill by gravity, with pumping stations where the ground does not cooperate.

There are two basic designs:

• Separate systems carry sewage in one set of pipes and street runoff in another. Sewage goes to the treatment plant; stormwater usually goes straight to a stream or harbor.
• Combined systems carry sewage and stormwater in the same pipes.⁸¹

In the US, EPA lists combined sewers as clustered in the Northeast and Great Lakes, including Illinois, Indiana, Maine, Michigan, New York, Ohio, Pennsylvania and West Virginia.¹³⁶ London's Victorian network, built by Joseph Bazalgette between 1859 and 1875, is a combined system too.¹³³

What is a combined sewer overflow?

A combined sewer works fine in dry weather. In wet weather, the mix of sewage and rain can exceed what the pipes or the treatment plant can handle, and the excess discharges untreated through relief outfalls into rivers, lakes and harbors.⁸¹ That discharge is a combined sewer overflow, or CSO.

The overflow is a designed relief valve. Without it, the same water would back up into basements and streets. The problem is what it carries.

How many US communities have combined sewers depends on which EPA page you read:

• EPA's current figure is about 700 communities.⁸¹ It goes with EPA's National CSO Inventory, first published in May 2023; about 90% of outfalls in it had been verified by state permitting authorities as of September 2023.¹³¹
• EPA's older Frequent Questions page, still online and updated in April 2026, gives about 860 communities serving about 40 million people.¹³⁶

The safest summary is about 700 US communities as of the 2023 inventory, down from the roughly 860 EPA long cited. The 40 million figure belongs to the older count; no EPA page pairs it with the 700.

The problem is not only American.

England's storm overflows, which are monitored under the Environment Agency's Event Duration Monitoring program, recorded 450,398 spills in 2024, for a record total of 3,614,427 hours, according to the Rivers Trust's analysis of the 2024 data.¹³⁷ That was 8,558 more hours than in 2023, though the average number of spills per overflow fell from 33 to 31.8.¹³⁷ The Environment Agency reported on March 26, 2026 that every storm overflow in England now has an event duration monitor, and that 2025 brought 291,492 spill events, 35% fewer than in 2024, or an average of 20.5 spills per overflow.¹³⁸

How is sewage treated?

Treatment happens in stages:

• Primary treatment holds sewage in tanks so solids settle and grease floats off.
• Secondary treatment uses bacteria to consume the dissolved organic pollution left behind.
• Tertiary or advanced treatment removes nutrients such as nitrogen and phosphorus, or polishes the water further for reuse.

An EPA-hosted training deck, "Wastewater Basics 101" by John R. Buchanan, defines the stages the same way: primary treatment is the separation of liquids from solids, secondary treatment supplies oxygen to aerobic microorganisms to "finish the job," and tertiary treatment is mainly nutrient removal.¹³⁹

The solids that settle out become sludge, which also needs treatment. At Boston's Deer Island plant, sludge goes into 12 egg-shaped anaerobic digesters, each about 130 feet (40 m) tall and 90 feet (27 m) across, sealed tanks where bacteria break it down without oxygen.¹⁴⁰ Since 1991, MWRA has shipped the digested sludge to a plant on the Fore River that turns it into fertilizer pellets.¹²⁴

At the far end of advanced treatment, some cities clean wastewater all the way back to drinking quality (for where drinking water usually starts, see Where your tap water comes from).

Singapore is the best-known example. Its national water agency, PUB, introduced NEWater to the public on August 9, 2002; it is made from treated used water by microfiltration, reverse osmosis and ultraviolet disinfection.¹⁴¹ PUB says NEWater and desalination together will meet up to 85% of Singapore's water demand by 2060.¹⁴² When its fifth NEWater plant opened in January 2017, NEWater was reported to meet 40% of Singapore's daily water demand.¹⁴³ The used water reaches the plants through the Deep Tunnel Sewerage System, a planned 206 km network that runs by gravity; its first phase, including a 48 km tunnel from Kranji to Changi, was finished in 2008, and the second phase is due to be commissioned in stages from 2027.¹⁴⁴

How do cities stop sewer overflows?

There are three broad options, and most large cities use all of them: separate the pipes, store the overflow until the plant can treat it, or keep rain out of the sewer in the first place. EPA's case studies show the range:¹³²

Indianapolis is building DigIndy, a 28-mile (45 km) tunnel system with a planned cost of $1.9 billion.¹⁴⁵

Deep tunnels also handle floodwater that has nothing to do with sewage.

North of Tokyo, Japan's Metropolitan Area Outer Underground Discharge Channel, often called G-Cans, diverts floodwater from smaller rivers to the Edogawa River.¹⁴⁶ Its tunnels total 6.3 km at a depth of about 50 m, and its surge tank is 177 m long, 78 m wide and 18 m high, held up by 59 pillars that each weigh 500 tons.¹⁴⁶ Construction began in March 1993, and from June 2006 water could flow all the way from the Otoshifurutone River to the Edogawa; four pumps can discharge up to 200 cubic meters a second.¹⁴⁶

What is green infrastructure?

EPA uses the Clean Water Act definition: green infrastructure means "plant or soil systems, permeable pavement or other permeable surfaces" that manage stormwater.¹³⁵ The everyday versions are rain gardens, planter boxes, green roofs and permeable pavements, which, in EPA's words, "help reduce and treat stormwater where it falls."¹⁴⁷

EPA's case for it is cost and scale. Green infrastructure "can be a cost-effective approach that reduces and treats stormwater at its source," it "can complement gray infrastructure to control CSOs," and it can shrink the size of the pipes, tanks and tunnels needed downstream, along with their operating and energy costs.¹³⁵ The word EPA uses is complement, not replace: every city on EPA's green-and-gray case study page combines the two.¹³²

Atlanta's version includes parks that double as storage. Historic Fourth Ward Park is built to hold stormwater, and Cook Park can hold up to 10 million gallons (about 38,000 cubic meters).¹³²

Each rain garden is small. The idea is that many of them together take the early part of a storm off the sewer, which lowers the odds that a combined pipe tips into overflow. (Rain is also central to How cities are adapting to a changing climate.)

London's super sewer: the Thames Tideway

London faces the same problem as Boston at a larger scale. Bazalgette's sewers, built from 1859 to 1875, were designed to overflow into the Thames, and by a 2011-based estimate the tidal river was receiving about 39 million cubic meters (about 10 billion gallons) of storm sewage a year.¹³³

The fix is the Thames Tideway Tunnel:

• 25 km (15.5 miles) long, from Acton in the west to Abbey Mills in the east, with a 7.2 m (24 ft) internal diameter.¹³³
• 30 to 70 m below ground, per Wikipedia; Thames Water gives a maximum depth of 67 m.¹³³¹⁴⁸
• It intercepts 34 of the most polluting CSOs on the Victorian network.¹³³
• It cost about £5 billion.¹³³

Construction began in 2016.¹³³ Thames Water marks the tunnel's connection to the Lee Tunnel in May 2024 as the key milestone; the last of 21 connections was finished in February 2025, and King Charles III officially opened it on May 7, 2025.¹⁴⁸¹³³ The dates describe different stages and are consistent with each other.

Tideway feeds the 7 km Lee Tunnel, completed in 2016, which runs from Abbey Mills to the Beckton treatment works and captures over 5 million tonnes of sewage a year.¹⁴⁸ Together, the two tunnels can hold 1.6 million cubic meters.¹⁴⁸ Thames Water expects spills at the intercepted outfalls to fall from over 50 a year to about five.¹⁴⁸

Our reading: Tideway is the closest parallel to Boston's approach. Both cities kept their old combined pipes and added deep storage and interception rather than digging up every street to separate them.

In Boston: from "harbor of shame" to Deer Island

Until 1991, Greater Boston's sewage sludge was discharged into its harbor.¹²⁴ The legal pressure began in 1982, when the city of Quincy sued; the Conservation Law Foundation and the US government followed with suits of their own.¹⁴⁹ Governor Michael Dukakis then proposed moving water and sewer functions out of the state's Metropolitan District Commission into a new agency.¹⁴⁹

The legislature passed MWRA's enabling act in 1984, and MWRA took over the water and sewer systems in 1985.¹²⁴ In 1986, federal Judge A. David Mazzone ordered a 13-year schedule to build a new treatment plant on Deer Island, and he oversaw the project for the court until 2004.¹²⁴

The harbor became national politics in the 1988 presidential race.¹⁴⁹ George H.W. Bush toured it and called it a "harbor of shame" in his campaign against Dukakis.¹³⁴

The rebuild came in stages:¹²⁴

• 1991: Sludge discharges to the harbor end; sludge goes to the Fore River pelletizing plant instead.
• 1995: New primary treatment begins at Deer Island.
• 1997 and 1998: The first two secondary treatment batteries start up; all three are running in the 2001-2005 period.
• 1998: The inter-island tunnel ends discharges from the Nut Island plant.
• 2000: The 9.5-mile Massachusetts Bay outfall opens.

Today Deer Island serves 43 communities, with an average flow of about 380 mgd (1.4 million cubic meters a day) and a peak capacity of 1.2 billion gallons a day.¹⁴⁰ Its outfall tunnel is 9.5 miles (15 km) long and 24 feet (7.3 m) across, and it releases treated water through 52 risers along its last mile, far out in Massachusetts Bay.¹⁴⁰

The ecological results are measurable. In studies from around 1984, liver tumors turned up in 8% to 15% of sampled winter flounder; after 2004 they were no longer detected.¹³⁴

What it cost depends on the source: Wikipedia's Deer Island article gives $3.8 billion, its Boston Harbor article gives $4.5 billion, and an article in The Conversation gives $4.7 billion, with different scopes and cost bases.^140149134 Call it roughly $4 billion. The same Conversation article values the resulting ecosystem services at $30 billion to $100 billion.¹³⁴

Boston's combined sewers have not gone away. MWRA's CSO program cut annual overflow volume by more than 2.8 billion gallons between 1987 and 2015, from about 3.3 billion gallons a year in the 1980s.¹²⁴ By subtraction, that leaves on the order of half a billion gallons a year still overflowing as of 2015.

How it changed

• 1859-1875: Bazalgette builds London's intercepting sewers, a combined system with overflows to the Thames.¹³³
• 1982: Quincy sues over Boston Harbor pollution.¹⁴⁹
• 1985: MWRA takes over Greater Boston's water and sewer systems.¹²⁴
• 1986: Judge Mazzone orders the Deer Island construction schedule.¹²⁴
• 1988: Boston Harbor becomes a presidential campaign issue.¹³⁴
• 1994: Milwaukee's deep tunnels begin keeping overflow out of Lake Michigan.¹³²
• 2000: Deer Island's Massachusetts Bay outfall opens.¹²⁴
• 2016: London's Lee Tunnel is completed and Tideway construction begins.¹⁴⁸¹³³
• 2023: EPA publishes its National CSO Inventory.¹³¹
• 2025: The Thames Tideway Tunnel becomes fully operational and is officially opened.¹³³

Taken together, the 19th-century goal was to get sewage away from houses as fast as possible, and rivers took the result. The late 20th century added treatment and legal deadlines. The current phase is about rain: storing it, slowing it, and keeping it out of the sewer.

What's changing now (2026)

• Tideway's first full years. London's super sewer has been fully operating since February 2025, and its performance against the target of about five spills a year at intercepted outfalls is the number to watch.¹³³¹⁴⁸
• US tunnel deadlines. Chicago's final reservoir is due in 2029, and DC Water's system-wide CSO reduction target of 96% is set for March 2030.¹³²
• The count keeps shrinking. EPA's current pages put the number of US combined sewer communities at about 700, down from the 860 it cited for years.¹³¹¹³⁶
• Green plus gray as the default. EPA's 2026 guidance pages present green infrastructure as a standard part of CSO control plans, alongside tunnels and tanks.¹³⁵¹⁴⁷
• Sewers as health sensors. Testing sewage to track disease in the population that flushed it has become a newer job for a very old system.

MWRA approved a pilot with Biobot in 2020 to test Deer Island wastewater for the virus that causes COVID-19.¹⁵⁰ Biobot had run an initial study at the plant in early March 2020, and MWRA's board then approved a $200,000 contract for a six-month pilot.¹⁵¹ It reports results separately for its North and South systems; as of mid-2026 sampling had dropped to once a week, Biobot testing was set to end in late July 2026, and the Massachusetts Department of Public Health planned its own twice-weekly program.¹⁵²

Nationally, CDC has run the National Wastewater Surveillance System since 2020, largely on one-time COVID-19 funds.¹⁵³ Water Online reported in February 2026 that the FY2026 spending law signed February 3, 2026 appeared to secure its funding, while the American Society for Microbiology wrote in April 2026 that CDC "will have no funding to sustain the national program beyond Sept. 30, 2026" and asked Congress for at least $120 million for FY2027.¹⁵³¹⁵⁴

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06How electricity gets to your building

The short version: Electricity is made at power plants, pushed at very high voltage along transmission lines, stepped down at substations, carried through neighborhoods on distribution feeders, and stepped down once more by a transformer on a pole, on a pad or in a vault under the sidewalk. In New England a separate operator, ISO New England, runs the high-voltage grid while local utilities such as Eversource own the wires to your door. Dense downtowns, including Boston's, use underground "network" systems that keep the lights on when one cable fails. After years of little growth, demand is rising again in 2026, pushed by data centers and expected to climb further with heat pumps and electric cars.

How does electricity get from the power plant to my house?

Think of the grid as four layers, each run at a different voltage.

• Generation. Power plants, wind farms and solar arrays make the electricity. New England's grid has nearly 400 dispatchable generators - plants an operator can call on or turn down - with about 29,300 megawatts (MW) of capability.⁵⁶
• Transmission. Step-up transformers at or near the plant raise the voltage so it can travel long distances. ISO New England counts about 9,000 miles (14,500 km) of high-voltage transmission line, which it defines as 115 kilovolts (kV) and above.⁵⁶
• Substations. These fenced yards full of transformers and switches step the voltage down and split the power into local circuits called distribution feeders.
• Distribution. Feeders run along streets on poles or in buried conduit. A distribution transformer - the gray can on a pole, the green box on a concrete pad, or a unit in an underground vault - lowers the voltage again to what a building uses.

The reason for all this stepping up and down is efficiency: for the same amount of power, a higher voltage means a lower current, and lower current loses less energy as heat in the wire. High voltage is good for moving power across a state and bad for a toaster, so the grid changes voltage at each handoff.

In most regions, primary distribution feeders run at roughly 4 to 35 kV. In North America, common choices are 12.47 kV, 13.8 kV, 24.9 kV and 34.5 kV, while 4.16 kV is typical of older systems.¹⁵⁵

What reaches the outlet also differs by region. Most of the world receives 220 to 240 volts at 50 Hz; North America is the main exception, where most premises get a split-phase supply offering 120 or 240 volts at 60 Hz.¹⁵⁶ Europe adopted a harmonized 230/400-volt standard under a 1997 amendment.¹⁵⁶

What's on a utility pole?

An overhead distribution pole is a stack of separate systems, and the order on the pole tells you who owns what. One rural electric cooperative's guide lists the parts roughly from top to bottom:⁵³

• Primary line. The high-voltage distribution wire coming from the substation, at the top of the pole.
• Insulators. Ceramic or polymer pieces that hold the live wires off the pole.
• Fused cutout. A switch with a fuse that isolates a faulted transformer so one failure does not take down the whole line. When a crew "re-fuses" a transformer after a storm, this is usually what they are replacing.
• Transformer. Steps the voltage down for nearby buildings.
• Service wire. The line that runs from the pole to the building.
• Ground wire. Runs the length of the pole and ties into the neutral.
• Guy wire. The angled cable anchored in the ground that keeps the pole from leaning.
• Automated switchgear. Some poles carry automatic switches (one brand is the "IntelliRupter") that can reroute power around a fault.
• Telecom lines. Phone, cable and fiber, lowest on the pole and hung without insulators. These belong to the phone and cable companies, not the electric utility.⁵³ (More on those in 311, the wires under the street, and city data.)

The guide's order is approximate, and real poles vary: streetlight circuits, the neutral and secondary wires usually sit between the transformer and the telecom space. A useful rule for anyone on the street is that the higher the wire, the more dangerous it is, and anything on a pole should be treated as live.

Utilities inspect this equipment on a schedule. Eversource told the Boston City Council in late 2025 that a third party inspects its Boston poles every five years, that it checks switches every year, and that it flies infrared surveys yearly to spot equipment running hot.⁴⁶

Why are there no power poles downtown?

Walk through the Financial District in Boston or Midtown Manhattan and you will rarely, if ever, see a distribution pole. The wires are under the street, and they are usually arranged differently from the radial feeders in the suburbs.

A suburban street typically hangs off one feeder: if that feeder fails, everyone on it goes dark until a crew switches them to another. Downtowns often use a secondary network instead. Many transformers in underground vaults all feed one interconnected low-voltage grid, so a fault on one supply is isolated without interrupting customers on the others.⁷⁷ These networks are used "in downtown areas of cities where there are many customers in a small area."⁷⁷ A large building can have its own spot network: two or more transformers dedicated to that one customer.⁷⁷

The key part in the vault is the network protector, a switch that opens automatically when power would flow backward from the shared grid into a primary feeder that has gone dead.⁷⁷ Without it, a failed feeder would be fed from the wrong end, which would be dangerous for the crews sent to repair it.

Networks are very reliable and very expensive, which is why they are generally reserved for places where the density of customers - and the cost of an outage - justifies the cost.

Why do manhole covers explode?

Underground cable avoids ice storms and falling trees but brings its own hazard. When cable insulation breaks down, it can arc and set off fires, smoke and, occasionally, explosions inside manholes. Utilities call these manhole events.

New York's Con Edison has published detailed figures. It runs more than 94,000 miles (151,000 km) of underground cable, which NBC News described as the largest such system in the world, and some Manhattan cable predates 1930.⁸⁴ In 2014 it recorded 3,369 manhole events, of which 32 were explosions in which a dislodged cover caused injury or damage.⁸⁴ Sixty-eight percent of the events came in January and February, when most road salt goes down, and nearly 90% were caused by cable insulation breaking down.⁸⁴

Salty meltwater soaks into the vaults and attacks old cable. Con Ed's response has included vented manhole covers, which let gases escape before pressure builds.⁸⁴

Those figures are from 2015 reporting; current counts were not in our sources.

Who runs the power grid?

In much of North America the company that sends you a bill does not run the regional grid. An independent system operator (ISO) or regional transmission organization (RTO) dispatches power plants, manages the high-voltage system and runs the wholesale electricity market for a region, while local utilities own and maintain the distribution wires.

ISO New England is the operator for the New England region. It serves about 15.1 million people and 7.6 million retail customers.⁵⁶ Its job, minute by minute, is to keep supply matched to demand. That job is hardest at peak demand, the moment when use is highest. New England's all-time peak was 28,130 MW, set on August 2, 2006.⁵⁶

Peaks still bite. On June 24, 2025, between 5 and 6 p.m., with temperatures at 97°F (36°C), the region hit 26,586 MW, its highest peak in more than a decade.⁸⁵ Reserves - the spare capacity kept ready in case a plant trips - ran short for more than three hours. The lights stayed on, but the shortfall triggered about $97.1 million in "Pay-for-Performance" charges, the market's penalty and reward system for generators that do or do not deliver when called.⁸⁵

Other regions organize this differently, and outside North America many countries have a national transmission operator rather than regional ones.

In the US, FERC regulates six such organizations - PJM Interconnection, the Midcontinent ISO (MISO), the California ISO (CAISO), the Southwest Power Pool (SPP), the New York ISO (NYISO) and ISO New England - which together manage transmission for about 190 million people.¹⁵⁷ Texas has its own operator, ERCOT, whose markets FERC does not oversee, and parts of the West and Northwest sit outside any RTO.¹⁵⁷ In Great Britain, the National Energy System Operator (NESO), an independent public corporation, runs the electricity system for the whole country. On the continent, ENTSO-E is an association of 40 transmission system operators from 36 European countries.¹⁵⁸

Who gets power back first after a storm?

Restoration follows a published order, and it explains why your street may stay dark while the next one comes back. Eversource lists its priorities this way:⁴⁸

1. Public-safety and life-threatening calls, such as live wires down near people.
2. Blocked roads with electrical hazards, so emergency vehicles can get through.
3. Critical facilities: hospitals, police and fire stations, and water and sewage plants.
4. Transmission lines, substations and main feeders, prioritized by how many customers each one affects.
5. Distribution repairs that restore the most customers soonest, with single-customer fixes near the end.

The logic is upstream first. Fixing the wire to one house does nothing if the feeder behind it is still down, and fixing one substation can bring back thousands of customers at once. The person whose service drop was torn off by a branch is, unluckily, at the end of the list.

Should power lines be buried?

After every big storm, someone asks why the wires are not underground. Undergrounding does protect lines from wind, ice and falling limbs, and it removes poles from sidewalks. The objection is cost.

At a December 2025 Boston City Council hearing, Eversource cited a 2023 range of about $2 million to $6 million per mile (about $1.2 million to $3.7 million per km) for undergrounding, and said inflation and the tight conditions of a dense neighborhood such as Charlestown could push costs higher.⁴⁶ Verizon cited about $300 per linear foot for its conduit alone.⁴⁶ The hearing followed a July 29, 2025 incident in Charlestown.⁴⁶

Part of the expense is that every system on the pole - power, phone, cable, fiber, streetlights - has to move too, and each owner needs its own trench space or conduit. Underground faults are also harder to find than a broken wire you can see from the street.

In Boston

Boston's electricity comes from the New England grid run by ISO New England, and the local wires belong to Eversource. Downtown Boston and parts of Cambridge are served by underground distribution networks rather than overhead lines; the City Council asked Eversource to explain why at its December 2025 hearing.⁴⁶ Eversource does not appear to publish how many networks or vaults it runs in Boston, or exactly which neighborhoods they cover.

Most of the rest of the city, including neighborhoods such as Charlestown, still has poles. That hearing put a price on burying them ($2 million to $6 million per mile in 2023 dollars) and laid out Eversource's inspection schedule: poles every five years, switches yearly and annual infrared flights.⁴⁶ Eversource also told the council it is installing advanced metering infrastructure (smart meters) and a distribution management system, the latter required by Massachusetts regulators at the Department of Public Utilities (DPU).⁴⁶ Both give the utility a live view of where power is flowing and where it has stopped, instead of waiting for customers to call.

When a nor'easter knocks out power, Boston restoration follows the same Eversource priority list described above: safety calls and blocked roads, then hospitals and water and sewer plants, then the big lines, then the long tail of individual homes.⁴⁸

How it changed

The first electric street circuits were lighting systems. Paris lit the avenue de l'Opéra with electric arc lamps on May 30, 1878, and Cleveland demonstrated 12 electric lights around Public Square on April 29, 1879.¹⁵⁹ Arc lamps gave way to incandescent bulbs, often wired on high-voltage series circuits, late in the 19th century.¹⁵⁹ (The street lighting side of this story is in How streetlights work.)

Underground cable followed in the densest cities. Some of the cable still in service in Manhattan predates 1930, which helps explain why insulation failures are so common there.⁸⁴

New England's peak of 28,130 MW in August 2006 still stands as of October 2026.⁵⁶ With the record holding for two decades, the recent upturn in demand stands out. The data center share of that demand was still small: US data centers used 58 terawatt-hours (TWh) in 2014.¹⁶⁰

What's changing now (2026)

Demand is climbing again, and the reasons differ by place.

Data centers. Lawrence Berkeley National Laboratory estimated that US data centers used 176 TWh in 2023, or 4.4% of US electricity, three times their 2014 use, and projected 325 to 580 TWh, or 6.7% to 12%, by 2028.¹⁶⁰ That range is wide because nobody knows how fast AI computing will grow.

Batteries. Grid storage is the fastest-growing piece of new capacity. US utility-scale battery capacity was 43.6 gigawatts (GW) at the end of 2025. Developers added 8.3 GW in the first half of 2026, bringing it to nearly 52 GW, with 14 GW more planned for the second half of 2026 and 26 GW for 2027.¹⁶¹ Batteries charge when power is cheap and plentiful and discharge into the evening peak.

Rooftop solar. New England has about 400,000 distributed solar installations totaling about 7,500 MW, mostly behind the meter: on homes and businesses, where they reduce the demand the grid sees rather than showing up as a power plant.⁵⁶ This helps explain why the June 2025 peak came at 5 to 6 p.m. rather than mid-afternoon: as the sun drops, rooftop output falls while air conditioners are still running.

Heat pumps. ISO New England forecasts total electricity demand growing about 1.0% a year through 2035, but winter peak growing about 2.9% a year.⁵⁶ Our reading of those numbers: as buildings switch from oil and gas heat to electric heat pumps, the coldest night of the year, not the hottest afternoon, may become the moment the grid is built for. New England could become a winter-peaking grid sometime in the 2030s.

For a city, the tight spot is often not the power plant but the last mile. Every block that adds EV chargers or electrifies its heating may eventually need a bigger transformer, a reinforced feeder or a new substation, which is why utilities are investing in the meters and management systems that show them where load is growing.

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07Gas under the street, and why steam comes out of it

The short version: Natural gas reaches buildings through a network of mains under the street and small service lines to each building, with regulators stepping the pressure down along the way. The gas has no smell, so utilities add a sulfur compound that smells like rotten eggs. Older cities are spending billions to replace leaking cast-iron and bare-steel pipe, and the 2018 Merrimack Valley explosions in Massachusetts showed what happens when a pressure system fails. The steam rising from manholes in New York and Boston is something else: district steam, made at central plants and piped under the street to heat buildings.

How does gas get to a building?

In outline, natural gas arrives in a city through high-pressure pipelines and is fed into a local distribution system of gas mains under the streets. A smaller service line runs from the main to each building. Along the way, regulators reduce the pressure so that what reaches a stove or furnace is gentle and steady.

A regulator needs to know the pressure downstream of it, and in many older systems it learns this through a small pipe called a sensing line (or control line). If downstream pressure drops, the regulator opens to let more gas through; if pressure rises, it closes. That simple feedback loop is safe as long as the sensing line reads the right pipe. The Merrimack Valley disaster, described below, happened when it did not.⁷¹

According to the US Pipeline and Hazardous Materials Safety Administration (PHMSA), the handoff from transmission pipeline to local system happens at the city gate, where the pressure is lowered and a sour-smelling odorant is added.¹⁶² From there, gas typically reaches distribution mains from a high-pressure source through a regulator station that lowers the pressure again.¹⁶³ In the Merrimack Valley system described below, 14 regulator stations each used two regulators in series, a "worker" and a backup "monitor."¹⁶³

What does a gas leak smell like?

Natural gas has no smell of its own. Utilities add mercaptan, a sulfur compound with a "rotten egg" smell, so that people notice leaks.¹⁶⁴ The standard advice is the same everywhere: if you smell gas, leave the building and call the utility or emergency services from a safe place.¹⁶⁴ The order matters because a light switch, a phone or a doorbell inside can make the spark that ignites gas, so the call waits until you are outside.

What is leak-prone pipe?

Much of the gas pipe under older American cities is cast iron or bare steel, which utilities and regulators call leak-prone pipe. Cast iron is brittle and can crack as the ground shifts and freezes, and steel without corrosion protection can rust through.

Massachusetts set up a formal program to replace it. A 2014 gas leaks law created the Gas System Enhancement Plan (GSEP), which lets utilities recover the cost of replacing leak-prone pipe through customers' bills.⁷⁹ The price has climbed fast. The cost per mile replaced rose from $1.32 million in 2015 to $3.46 million in 2025.⁷⁹ As of 2025, 4,049 miles (6,500 km) of leak-prone pipe remained in the state, and finishing the job by replacement alone would cost an estimated $13.7 billion more.⁷⁹

In May 2025 the state Department of Public Utilities (DPU) cut the cap on how much GSEP can add to revenue, from 3% toward 1.5% by 2027, and told utilities to consider repairs and non-pipeline alternatives instead of automatically replacing every old main.⁷⁹ Massachusetts had about 1.7 million gas customers in 2019, 91% of them served by National Grid or Eversource.⁷⁹

The debate behind those numbers runs like this. Replacing old pipe makes the current system safer and reduces leaks of methane, a potent greenhouse gas. But the state is also pushing buildings to switch to electric heat. A new main is expected to last for decades, and if fewer customers use gas over that time, the remaining ones may end up paying for pipes that carry less and less. Utilities, regulators, climate groups and ratepayer advocates weigh those two goals differently.

What happened in the Merrimack Valley in 2018?

At about 4 p.m. on September 13, 2018, high-pressure gas poured into the low-pressure distribution system serving Lawrence, Andover and North Andover, Massachusetts, north of Boston.⁷⁰ Fires and explosions damaged 131 structures and destroyed at least five homes. One person was killed and 22 people were taken to hospitals, including three firefighters.⁷⁰ Columbia Gas of Massachusetts shut down the low-pressure system, cutting off 10,894 customers.⁷⁰

The US National Transportation Safety Board (NTSB) traced the cause to a pipe-replacement job. A crew working for Columbia Gas, which was owned by NiSource, was replacing an old cast-iron main. They abandoned the old main while the sensing lines for the area's regulators were still attached to it.⁷⁰ With the old pipe out of service, the sensing lines read falling pressure, and the regulators did what they were designed to do: they opened fully, sending high-pressure gas into the neighborhood system.⁷¹ The work package "did not account for the location of the sensing lines."⁸⁶ Columbia Gas' monitoring center in Columbus, Ohio, received the high-pressure alarms.⁸⁶

On September 24, 2019, the NTSB determined the probable cause: weak engineering management and oversight by Columbia Gas, and a low-pressure system without adequate overpressure protection.⁷¹ The board called systems that rely only on sensing lines and regulators "not optimal" and found NiSource's engineering risk management deficient.⁷⁰

Our reading: the disaster happened during work meant to make the system safer, which is a reminder that replacing old pipe carries risks of its own and depends on accurate records of what is connected to what.

The person killed was Leonel Rondon, 18.¹⁶⁵ According to PHMSA, the low-pressure system was meant to run at 0.5 pounds per square inch (psi), about 12 inches of water column, and its regulator stations stepped gas down from roughly 75 psi.¹⁶³

Why does steam come out of the street?

In Manhattan, and on a smaller scale in Boston, the white plumes rising from manholes and from tall orange-and-white striped tubes are usually not a gas leak or a sewer problem. They come from district steam: steam made at central plants and piped under the streets to heat many buildings.

New York's system is among the oldest and largest in the US. The New York Steam Company began service on March 3, 1882, and merged into Con Edison in 1954.¹⁶⁶ As of 2025, Con Ed's steam system had about 105 miles (169 km) of mains running from 96th Street to Battery Park and serves about 1,500 customers.¹⁶⁷ About 27 billion pounds of steam flow through it each year.¹⁶⁶

The visible vapor has two usual sources. Groundwater or rainwater that touches a hot steam pipe boils off, and small leaks in the pipes themselves release steam.¹⁶⁶ Con Ed vents that vapor through 10-foot (3 m) orange-and-white stacks placed over manholes, so it rises above pedestrians and drivers instead of blinding them at street level.¹⁶⁶

The pipes can also fail badly. Steam pipe explosions hit Midtown Manhattan in 2007 and the Flatiron District in 2018, when dozens of buildings were evacuated (Wikipedia gives both 49 and 28).¹⁶⁶

Steam does more than heat. In New York, Con Ed steam is used in restaurant kitchens and to power absorption chillers for air conditioning.¹⁶⁸ US district energy supplier Vicinity Energy says hospitals on its systems use its high-pressure steam for space humidification, to support infection control.¹⁶⁹ Steam systems like New York's belong to the first generation of district heating, introduced in the US in the 1880s; later generations, starting in the 1930s, switched to pressurized hot water, and the common heat carrier today is water rather than steam.¹⁶⁸

In Boston

Gas. Boston's gas history begins with light. The Boston Gas Light Company was chartered on January 22, 1823, and the city's first public gas street lamp was lit in Dock Square, near Faneuil Hall, on January 1, 1829.¹⁷⁰ Today the city's gas customers are part of the Massachusetts system described above, where National Grid and Eversource serve most of the state's roughly 1.7 million gas customers and the GSEP program pays to replace leak-prone mains.⁷⁹ The city still burns gas in about 2,800 street lamps; that story is in How streetlights work.

Steam. Boston and Cambridge share a district steam system now run by Vicinity Energy. Vicinity says it has served Boston for "over 90 years."⁹⁷ The system's size depends on which source you read, and they disagree:

Vicinity's own page gives both sets of pipe and building figures.⁹⁷ The larger numbers may describe Boston and the smaller ones Cambridge, but the page does not say so. Canary's figures come from its reporting on the system.⁵⁵ Either way, roughly 70 million square feet (6.5 million square meters) of buildings take heat from these pipes.

Much of that steam has come from the Kendall Cogeneration Station in Cambridge, a plant about 75 years old.⁵⁵ Emerson College and the life-science developer IQHQ have committed to buying its lower-carbon steam.⁵⁵

How it changed

Gas networks were built first for light, not heat. In London the Gas Light and Coke Company, the world's first gas company, received a royal charter in 1812, and by the 1820s London had about 50,000 gas lamps fed by roughly 300 miles of pipe.¹⁷¹ Boston followed with its 1823 charter and 1829 Dock Square lamp, but grew slowly: by 1839 it had only about 180 gas street lamps.¹⁷⁰

District steam arrived in the 1880s with the New York Steam Company in 1882.¹⁶⁶

The modern regulatory era in Massachusetts runs through two events: the 2014 gas leaks law that created GSEP,⁷⁹ and the 2018 Merrimack Valley explosions, followed by the NTSB's 2019 finding on cause.⁷¹

What's changing now (2026)

Gas: replace, repair or retire. Massachusetts regulators are no longer assuming that every old main should be replaced with a new one. The DPU's May 2025 order lowering the GSEP cap and pressing utilities to consider repairs and non-pipeline alternatives reflects the rising cost of replacement - $3.46 million a mile in 2025 - and the $13.7 billion still needed to finish.⁷⁹ That leaves a question for the next decade: how much to spend on a gas network that the state's climate policies aim to shrink.

Steam: moving to electricity. Both big US steam systems are trying to stop burning so much fuel.

• In Boston and Cambridge, Vicinity finished a 42 MW electric boiler at Kendall in 2024 and is selling what it calls eSteam, steam made with electricity rather than by burning fuel on site.⁵⁵⁹⁷ It has begun building a 35 MW heat pump that will draw heat from the Charles River, expected in mid-2028.⁵⁵⁹⁷
• In New York, Con Ed says direct emissions from its steam system are down 60% since 2005, and it is piloting heat pumps, electric boilers and thermal storage, aiming for measurable emissions cuts around 2035.¹⁶⁷

Electric steam shifts the emissions question onto the power grid (see How electricity gets to your building). A 42 MW boiler is a large new load on a grid that is also absorbing heat pumps and electric cars.

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08How streetlights work, from gas lamps to LEDs

The short version: Street lighting has gone from oil lanterns to coal-gas lamps, electric arc lamps, incandescent bulbs, the orange glow of sodium lamps and, since the 2000s, LEDs. Most streetlights switch on by themselves, using a small light sensor or a timer that calculates sunset. LEDs cut energy use sharply but raised new arguments about glare, blue light and dark skies, and a batch of faulty fixtures turned streetlights purple across North America. Boston owns about 71,000 streetlights, including about 2,800 gas lamps.

How it changed

Oil. Ancient Greek and Roman cities used oil lamps, and France introduced an improved oil street lantern, the réverbère, in 1745.¹⁵⁹

Gas. On June 4, 1807, Frederick Albert Winsor gave the first public demonstration of gas street lighting on Pall Mall in London.¹⁵⁹ The display marked King George III's birthday, and the pipes were old musket barrels.¹⁷¹ The Gas Light and Coke Company, the world's first gas company, received a royal charter in 1812, and by the 1820s London had about 50,000 gas lamps on roughly 300 miles (480 km) of pipe.¹⁷¹ Gas lit Westminster Bridge on December 31, 1813, and the main streets of Paris from 1829.¹⁵⁹ Lighting all those lamps was a job: by the London Museum's count, the Victorian city had more than 25,000 lamplighters.¹⁷¹

Electric arcs. Pavel Yablochkov's arc "candle" dates to 1875. Paris installed electric street lights on the avenue de l'Opéra on May 30, 1878; Cleveland demonstrated 12 electric lights around Public Square on April 29, 1879; and Wabash, Indiana, hung four Brush arc lamps over its courthouse on February 2, 1880.¹⁵⁹ An arc lamp makes light from a spark jumping between two carbon rods. Arc lamps were harsh and needed frequent electrode replacement, and late in the 19th century incandescent lamps, often wired on high-voltage series circuits, replaced them.¹⁵⁹

Discharge lamps. In the 20th century, cities moved to lamps that make light by passing current through a gas or vapor. Low-pressure sodium became common after World War II, and high-pressure sodium became the preferred type in the late 20th century.¹⁵⁹ High-pressure sodium (HPS) is the orange-pink light that many people still picture when they think of a city at night.

The high-pressure mercury-vapor lamp came out of work in the 1920s and was widely used for street lighting by the 1930s.¹⁷² High-pressure sodium was demonstrated in a laboratory in 1959, and the first commercial HPS lamps came from companies in the US, UK and the Netherlands in 1965.¹⁷³

LEDs. A light-emitting diode (LED) is a semiconductor light source that uses far less energy than older lamps and lasts much longer. Ann Arbor, Michigan, is cited as the first US city to fully implement LED street lighting, in 2006, and Mississauga, Canada, converted more than 46,000 lights between 2012 and 2014.¹⁵⁹ "First" claims like Ann Arbor's are hard to pin down, and others may dispute it.

How do streetlights turn on at night?

In most places, nobody flips a switch. Most streetlights control themselves in one of a few ways:¹⁵⁹

• Photocell. A small light sensor, usually a button or puck on top of the fixture, switches the lamp on at dusk and off at dawn. It also turns lights on under heavy cloud.
• Astronomical timer. A controller that calculates local sunrise and sunset for each day of the year and switches the lights accordingly.
• Solar dials. An older mechanical method that tracked the changing length of the day.
• Networked controls. Newer systems put a communicating node on each light, letting a city monitor lights remotely, dim them and detect faults automatically.

Some councils, notably in Britain, use "part-night" lighting, switching lights off between about midnight and 5:30 a.m. to save energy.¹⁵⁹ London's surviving gas lamps still run on mechanical clock timers.¹⁷¹

A streetlight that burns all day often has a failed photocell or a controller stuck in the on position. On a networked system, the city sees that fault on a screen; on an older one, it waits for someone to report it.

Why are LED streetlights so harsh and blue?

The switch to LEDs was driven by energy savings. Boston says its LED conversion cut energy use and emissions by 60%, and that LEDs last about three times longer than the lamps they replaced.⁷²

The first wave of LED streetlights, though, gave off a cold, blue-white light, and residents in many cities complained about glare. The measure for this is color temperature, given in kelvins (K): lower numbers look warm and yellow, higher numbers look cool and blue-white. The debate in the 2010s was over fixtures at 4000K and above.

At its June 2016 annual meeting, the American Medical Association (AMA) adopted guidance urging communities to minimize blue-rich lighting and to choose 3000K or lower rather than 4000K.¹⁷⁴ It cited glare, reduced visual acuity and suppression of melatonin, a hormone linked to sleep.¹⁷⁴ The AMA did not tell cities to avoid LEDs, and the US Department of Energy continued to promote LEDs for their energy savings.¹⁷⁴ In our reading, the AMA's health claims are best treated as guidance rather than settled science, and the practical outcome has been a push toward warmer fixtures rather than away from LEDs.

Industry and government replied within weeks. The DOE published "Get the Facts: LED Street Lighting," saying low color temperatures "may be beneficial for reducing nonvisual impacts, but they may also reduce the effectiveness of the lighting."¹⁷⁵ The National Electrical Manufacturers Association (NEMA) agreed that spectral content should be one factor in outdoor lighting but said "a single solution is simply not appropriate for all situations."¹⁷⁵

Dark-sky advocates make a related argument about wildlife, astronomy and wasted light. DarkSky International sets out five principles for responsible outdoor lighting: it should be useful, targeted, low level, controlled and warm-colored.¹⁷⁶ The principles do not name a specific kelvin figure.¹⁷⁶ In practice that means a full-cutoff or shielded fixture that sends light down rather than up or sideways, at no more brightness than the task needs, on a timer or dimmer, in a warm color.

Why did streetlights turn purple?

Starting in early 2021, people across North America began noticing streetlights glowing violet. The cause was a manufacturing defect.¹⁷⁷

A white LED is usually a blue-violet LED chip coated with a phosphor, a material that converts some of the blue light into yellow so the mix looks white. In some LED packages the phosphor layer degraded or peeled away, letting the raw blue-violet light through.¹⁷⁷ The affected fixtures were American Electric Lighting (AEL) products from Acuity Brands, made roughly between 2017 and 2019.¹⁷⁷

By 2022, reports had come from at least 30 US states.¹⁷⁷ Places named include Massachusetts (Boston and Interstate 93), South Florida, Milwaukee, Schaumburg in Illinois, Los Angeles, Bend in Oregon, Vancouver and Ireland.¹⁷⁷ Acuity's warranty and recall expenses were $32.3 million in 2021, $47.0 million in 2022 and $52.4 million in 2023.¹⁷⁷ Those totals cover all of the company's warranty and recall costs, not only purple lights, so they are an upper bound on what the defect cost rather than an exact figure.

Residents can report purple lights through utility portals so the fixtures are replaced under warranty.¹⁷⁷

Who owns the streetlights?

It depends on the place, and it determines who you call when one goes dark. In Boston the city owns and maintains its streetlights through the Public Works Street Lighting Division, and residents report problems through the city's 311 service (more on 311).⁷² Where a utility owns the lights, residents report problems, including purple lights, through the utility's portal.¹⁷⁷

In Massachusetts, Chapter 164, Section 34A of the General Laws, adopted as part of the 1997 Restructuring Act, lets municipalities buy their streetlights from the utility. The Metropolitan Area Planning Council says buying the lights alone can save 30-60% of streetlighting costs, and up to 70-80% when combined with an LED retrofit.¹⁷⁸

In Boston

The system. Boston has about 71,000 streetlights, including about 2,800 gas lights and 1,500 fire-alarm lights, in 19 fixture types, all maintained by the Public Works Street Lighting Division.⁷² The fire-alarm lights likely mark the city's street fire-alarm boxes (more on those in From fire alarm boxes to 911). An older, undated city page gave a smaller total of about 67,000 lights and described what is underneath them: 4 million feet of conduit, 18 million feet of cable, 1,600 control boxes and 32,000 pull boxes.⁷⁶ That page also says fixtures designed since 2000 are "medium cut-off," aiming 95% of their light down.⁷⁶

LEDs. Boston began converting to LED in fall 2010.⁷² By 2022 about 85% of the city's lights were LED.¹⁷⁹ Purple LED streetlights were reported in Boston and along I-93 during the early-2020s phosphor failures.¹⁷⁷

Reporting a dark light. Use 311 (311.boston.gov) or call 617-635-5810.⁷²

The gas lamps. Boston was early to gas (the pipes are covered in Gas under the street, and why steam comes out of it). The Boston Gas Light Company was chartered on January 22, 1823, and the first public gas street lamp was lit in Dock Square, near Faneuil Hall, on January 1, 1829.¹⁷⁰ Growth was slow at first: by 1839 the city had only about 180 gas lamps.¹⁷⁰

Gas lamps survive today in larger numbers than most visitors expect. In 2022 Boston had about 2,800, more than 1,000 of them on Beacon Hill.¹⁷⁹ Many are 1960s replicas rather than 19th-century originals.¹⁷⁹ The cost adds up: nearly $1 million a year in gas plus about $200,000 in maintenance, and nearly 5,000 metric tons of greenhouse gas emissions a year, about 3.4% of the city government's operational emissions.¹⁷⁹

In 2022 the city began testing a replacement. The first LED "faux gas" lamp, built to look like a gas lantern, went up in Bay Village in March 2022.¹⁷⁹ Not everyone wanted the change: the Beacon Hill Civic Association objected in January 2022.¹⁷⁹ The city frames the issue as emissions and cost; preservation-minded residents frame it as the character of historic streets. Both are describing real things.

For comparison, London has about 1,300 surviving gas lamps, maintained by five British Gas lamplighters.¹⁷¹ On those figures, Boston has roughly twice as many.

What's changing now (2026)

As of the city's May 6, 2026 update, Boston still lists about 2,800 gas lights among its 71,000 streetlights, and describes LED conversion as a program that began in 2010.⁷² That is the same figure the city gave in 2022, so on its own count the gas-to-LED conversion that began with the Bay Village pilot has not yet much reduced the number of gas lamps.

When the conversion was announced in March 2022, the city said the 2,800 gas lamps were 4% of its streetlights but 37% of streetlight emissions, and cost nearly $1 million a year in gas plus about $200,000 in maintenance. At the time, it was also exploring smart lighting for non-historic streetlights.¹⁸⁰ Boston's Smart Utilities standards list energy management for street light networks among the technologies for projects that rebuild sidewalks.¹⁸¹

Three broader trends run through the sources above:

• Warmer color. After the 2016 AMA guidance and dark-sky campaigns, cities increasingly specify warmer LEDs than the first wave.¹⁷⁴¹⁷⁶
• Controls. Networked nodes allow remote monitoring, dimming and automatic fault detection, so that the city, not a resident, can be the first to know when a light fails.¹⁵⁹
• Cleanup of the purple fixtures. Acuity's warranty and recall costs rose each year from 2021 to 2023, and affected lights are replaced under warranty when reported.¹⁷⁷

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09How traffic lights work

The short version: A traffic light is a small computer in a roadside cabinet, a set of sensors that tell it who is waiting, and a separate safety box that will switch the whole intersection to flashing if anything looks wrong. The computer divides time into phases, using a diagram engineers call rings and barriers, so that conflicting movements are never green together. Many city signals run timing plans set from traffic counts and pushed out from a control room; some retune themselves continuously. Whether the crosswalk button does anything depends on where and when you press it.

How it changed: from a gas lamp in London to a computer on every corner

The first traffic signal stood outside the Houses of Parliament in London, near the House of Commons at Great George Street and Bridge Street.¹⁸² It was designed by John Peake Knight, a railway signaling engineer, and borrowed the railway's vocabulary: semaphore arms by day, red and green gas lamps by night, worked by hand by a police constable.¹⁸³ Sources disagree on the exact day it went up: Wikipedia gives 9 December 1868 and History Hit gives 10 December 1868.¹⁸⁴¹⁸³ It did not last.

A gas leak caused it to explode in 1869 - Wikipedia dates this to 2 January - and the policeman on duty was badly injured.¹⁸²¹⁸⁴ History Hit says the operator was "reportedly" killed, but the more careful sources say injured.¹⁸³ The signal was gone by 1870.¹⁸²

Electricity brought the idea back. In Salt Lake City, police officer Lester Wire developed an early electric traffic light in 1912.¹⁸⁴ On August 5, 1914, Cleveland's safety director Alfred Benesch tested a red and green signal from the American Traffic Signal Company at East 105th Street and Euclid Avenue. Lights about 15 feet (4.5 m) up on four corner poles showed "stop" and "move"; an officer in a booth threw the switches by hand, and bells rang to warn of a change, twice for Euclid and once for East 105th.¹⁸⁵

Yellow arrived in Detroit in 1920. William L. Potts (1883-1947), a Detroit police officer, designed the first three-color, four-direction signal, installed at Woodward Avenue and Fort Street.¹⁸⁶ Earlier lights had only red and green; three colors were standard by the mid-1930s.¹⁸⁶

Linking signals together came almost as early as the signals themselves. Salt Lake City tied six intersections to one manual switch in 1917; in 1922 Houston added automatic timers made by Crouse-Hinds; in 1952 Denver used one computer to control 120 lights; and in 1967 Toronto ran 159 signals from computers that took in vehicle detection.¹⁸⁴ Britain trialed automatic signals in Wolverhampton's Princes Square in 1927 and installed its first permanent ones at Park Row and Bond Street in Leeds in March 1928.¹⁸⁴

Did Garrett Morgan invent the traffic light?

No, though he did invent a traffic signal, and the distinction matters. Garrett Morgan, a Black inventor and businessman,¹⁸⁷ was granted US Patent 1,475,024 for a three-position traffic signal on November 20, 1923.¹⁸⁴ His design was a manually operated post with "stop" and "go" arms, cranked by an attendant. Its third position stopped traffic in all directions so the intersection could clear, and he sold the rights to General Electric for $40,000.¹⁸⁷¹⁸⁵ The Cleveland Police Museum notes that two-way stop-and-go signals already existed when Morgan designed his.¹⁸⁵

So the popular claim that Morgan invented "the traffic light" or "the yellow light" does not hold up: London had a signal in 1868, Salt Lake City and Cleveland had electric ones by 1912 and 1914, and Potts' three-color light dates from 1920. In our reading, the accurate version is still a good story. Morgan patented and commercially licensed a signal with an all-stop position, a feature that resembles the all-red clearance time modern signals still use, and he did it as a Black businessman in 1920s America. He deserves credit for that, not for an invention that predates him.

What's in the box on the corner?

A signalized intersection has three working parts you can see from the sidewalk:

• Signal heads: the housings on poles or mast arms that hold the red, yellow and green lights.
• The controller cabinet: the gray or green metal box at one corner, holding the electronics.
• Detectors and push buttons: the sensors that tell the cabinet who is waiting.

Inside the cabinet is the controller, the intersection's "brains": a small, ruggedized computer that decides which movements get green and for how long.⁷⁴ Next to it sit load switches, which turn the controller's 12-volt DC logic signals into the 120-volt AC power that lights the lamps, plus a flasher that produces flashing operation.⁵⁰

US controllers come from two family trees. NEMA TS 1 (1976) defined basic actuated control so equipment from different makers was interchangeable, and NEMA TS 2 (1992) added a serial data link and defined coordination and preemption. A parallel line ran from the hardware-only Type 170 to Caltrans' Model 2070 (1995), which also defined the processor, operating system and software language. The current Advanced Transportation Controller (ATC) family is meant to merge them in an open architecture.⁵⁰

The lamps changed around 2000. A paper from that time put LED signals at roughly 80-90% less energy than incandescent bulbs, lasting about 5-10 years instead of about one; about 400,000 LED modules were then installed in the US, out of roughly 11 million signal lamps.¹⁸⁸ We found no current count of how far LEDs have spread since. (Streetlights went through a similar switch; see How streetlights work.)

Why do traffic lights flash red?

The most important box in the cabinet is the one that does not run the intersection. The conflict monitor (in TS 1 cabinets) or malfunction management unit, or MMU (in TS 2), is separate hardware that watches the controller's outputs independently.⁷⁴⁵⁰ If it ever sees two conflicting movements green at once, or voltages that should not be there, it overrides the controller and puts every signal head into flash.⁷⁴

This is the fail-safe: the worst a computer fault should produce is a flashing intersection, never green both ways. In the US, agencies commonly set the flash either to red on every approach, which drivers treat as an all-way stop, or to yellow on the main road and red on the side streets.

Delaware's state edition of the MUTCD, for example, recommends flashing yellow for the major street and flashing red for the other approaches unless flashing red is used on all of them, and requires every green indication to go dark during flash.¹⁸⁹ State traffic law gives flashing red the force of a stop: Iowa's code says a flashing circular red means traffic shall stop, then may proceed cautiously while yielding to vehicles not required to stop, and a flashing yellow means proceed with caution.¹⁹⁰

Flash is also used on purpose. Many Boston signals flash overnight, when traffic is light.⁴⁷

Phases, rings and barriers, explained without the jargon

A signal divides time into phases, each a block of time serving a set of movements that can safely go together, such as northbound and southbound through traffic. One full trip through all the phases is the cycle length.¹⁹¹ Each phase's share of the cycle, including its yellow and all-red clearance time, is its split.¹⁹¹

US engineers draw this with the NEMA ring-and-barrier diagram. A ring is "a sequence of two or more conflicting movements" timed one after another; a typical controller runs two rings side by side, each with up to four phases.¹⁹² A barrier is a point where the two rings must line up, so that conflicting movements in different rings are never selected and timed together.¹⁹²

In plainer words: think of the left side of the barrier as "main street's turn" and the right side as "side street's turn". On the main-street side, ring 1 might serve the southbound left turn and then northbound through traffic, while ring 2 serves the northbound left and then southbound through traffic. Each ring can move at its own pace - a busy left-turn lane can get more time than the opposite one - but both rings have to arrive at the barrier together before the side street gets anything. That is how the controller stays flexible without ever giving a left-turning car a green into oncoming traffic.

There are two broad ways to run the clock:

• Pretimed (fixed-time) control serves every phase every cycle for a set time regardless of traffic. It is typical in closely spaced downtown grids.¹⁹²
• Actuated control uses detectors to decide whether a phase is served and how long it lasts. Fully actuated signals have detection on every approach.¹⁹² Many real intersections mix the two: a coordinated main street, with side streets and left arrows served only on demand.

What are the cut lines in the pavement at a red light?

Those rectangles, diamonds or circles of sealed saw cuts near the stop line are usually inductive loops. Wire is laid in slots sawed into the pavement and sealed over.¹⁹³ When a vehicle sits above the loop, its metal reduces the loop's inductance, which raises the frequency of an oscillator in the detector electronics; the detector card in the cabinet reads that change as a "call".¹⁹³

Agencies also use other sensors, each with trade-offs:¹⁹³

A loop's weak point is anything with little metal. A bicycle may not register on a loop that is not set sensitively enough, which is why people on bikes sometimes wait at a red that never changes, and why some cities paint a symbol showing where to stop a bike over the loop.

Do crosswalk buttons actually work?

Sometimes. In busy downtowns, many signals use pedestrian recall: the walk signal comes up automatically every cycle, so the button has no effect on timing. Boston uses recall in its busy pedestrian areas.⁴⁷ In 2017 the Boston Globe reported that "the vast majority" of buttons in Boston's downtown neighborhoods do nothing by design; some are inactive by day but work overnight, buttons outside downtown generally work, and the dead ones remain because removing them costs money.¹⁹⁴ The same report said New York City had removed several hundred nonfunctioning buttons in areas under reconstruction but kept others.¹⁹⁴

In 2020 Brookline, Massachusetts deactivated push buttons at 55 signals, and Cambridge and Arlington followed; Providence made its change permanent.¹⁹⁵ MassDOT kept the buttons working at its roughly 1,400 pedestrian signals, and Boston pointed out that many downtown signals already gave the walk automatically.¹⁹⁵

In a dense core during the day, the button often does nothing because the walk is already coming. In suburbs, at night, and at mid-block crossings, it usually does call the walk signal. On an accessible signal, pressing the button can still matter even where timing is automatic, because it can trigger the audible and vibrating cues described below. Countdown timers, which spread in the 1990s, are now required in the US on new or upgraded signals at wider crossings; US rules prohibit countdowns for drivers.¹⁸⁴

Leading pedestrian intervals and accessible signals

A leading pedestrian interval (LPI) is "a brief (3-7 second) advance WALK indication" before parallel traffic gets its green.¹⁹⁶ The head start puts people a few steps into the crosswalk, where turning drivers can see them, before cars move. FHWA studies cited by Caltrans show a 13% reduction in pedestrian-vehicle crashes at intersections that use them.¹⁹⁶

An accessible pedestrian signal (APS) is a crossing device for blind and low-vision people. Boston's specification shows what one does: a locator tone about 0.15 seconds long, repeating every second and adjusting its volume to street noise, so a person can find the button; a button that vibrates during the walk; an arrow pointing in the direction of the crossing; and an optional spoken message. The messages can be programmed over Bluetooth.¹⁹⁷

In American Council of the Blind v. City of New York, a federal court ordered New York City to install APS at 10,000 intersections within 10 years and at all signalized intersections by 2036.¹⁹⁸ At the time, about 749 intersections, about 5%, had them, out of more than 13,200 signalized intersections; the same advocates' page also gives 13,430.¹⁹⁸

How do green waves work?

A green wave, which engineers call progression, is a string of signals timed so that a vehicle at the planned speed meets green after green. Three numbers make it work.¹⁹¹

• The signals must share a cycle length, or a multiple of it (a quiet intersection can run two cycles for each one at a busy neighbor, which is called double-cycling).
• Each signal has an offset: the time between a master clock reference and the start of its own green, in seconds or as a percent of the cycle.
• The resulting bandwidth is the window of time in which vehicles can travel through the whole system at the set speed.

FHWA's 2008 timing manual prefers that cycles at conventional four-leg intersections "not exceed 120 seconds".¹⁹¹ Plans are usually built from a software model of the corridor.⁷⁴ A green wave is easiest on a one-way street. On a two-way street with uneven block spacing, the timing usually has to favor one direction, often inbound in the morning and outbound in the evening. Many city signals run a few time-of-day plans (morning, midday, evening, overnight) switched by the clock.

Adaptive systems: signals that retune themselves

Adaptive signal control goes a step further and recalculates splits, cycle lengths and offsets continuously from live detector data. The two best-known systems date from the 1970s:

• SCATS, developed in 1975 by the New South Wales Department of Main Roads in Sydney, was "one of the first adaptive control systems to be available commercially". Its operator says it now runs at more than 65,000 intersections in 218 cities in 33 countries.¹⁹⁹
• SCOOT (Split Cycle Offset Optimisation Technique) was developed by the UK's Transport Research Laboratory in 1979 for the Department of Transport. It uses loop data to adjust splits, cycle times and offsets by region, with about a 15% improvement over fixed timing.²⁰⁰ Transport for London is replacing SCOOT with a newer system called FUSION, targeting 500 sites by 2025/26 and 4,350 by 2030/31.²⁰⁰

Adaptive systems are only as good as their detectors and their maintenance. They tend to help most where traffic is variable and hard to predict - around stadiums, malls or highway ramps - and add less where a well-tuned time-of-day plan already fits the traffic.

Preemption and bus priority

Preemption interrupts the normal cycle to give an immediate green to an emergency vehicle (the dispatch side is in From fire alarm boxes to 911) or to clear traffic off a railroad crossing, while showing red to conflicting movements.⁷⁴ One early documented case: in Houston in 1991-92, emitters on emergency vehicles that triggered signals within a quarter mile (400 m) at 22 intersections cut average emergency travel time by 16% and 23% in two fire districts.²⁰¹ The cost is that a preempted signal falls out of step with its neighbors and needs time to rejoin the green wave.

Transit signal priority (TSP) is gentler. The controller holds a green a few seconds longer or cuts a red a few seconds shorter for an approaching bus, staying within its normal pattern. In Boston, the city and the MBTA started a pilot in July 2024 at three intersections on Brighton Avenue (at Harvard, Linden and Allston streets) for bus routes 57 and 66. Bus waiting time at red lights fell 21%, and the two agencies announced an expansion.⁹⁴ (More on the buses themselves in How the subway and the bus actually run.)

Right turn on red

In most of the US, a driver may turn right on red after stopping unless a sign says otherwise. That became national rule because of the 1970s energy crisis: the Energy Policy and Conservation Act of 1975 effectively required states to allow right turn on red (RTOR) to keep federal energy assistance, and a 1992 amendment extended the idea to left turns on red from a one-way street onto another one-way street.²⁰² New York City has long prohibited it more broadly.²⁰²

The safety cost appeared quickly. A 1982 study in the Journal of Safety Research found that after mid-1970s adoption, pedestrian crashes involving right-turning vehicles rose 48% in New York State, 107% in Wisconsin, 57% in Ohio and 82% in New Orleans, and bicycle crashes of that type rose 72-82%. Drivers look left for a gap in traffic and miss people approaching from the right. Those crashes were 1-3% of all pedestrian and bicycle crashes.²⁰³

The debate reopened in the 2020s. A December 2024 Mineta Transportation Institute study found that most drivers roll through rather than stop, and recommended that states let cities ban RTOR by default and allow it only at selected intersections.²⁰⁴ New York City mostly prohibits it, except in parts of Staten Island.²⁰⁴ The rule is less common elsewhere: in much of Europe, turning on a red signal is not allowed unless a specific sign or arrow permits it.

Roundabouts: the intersection without a light

Sometimes the best signal is no signal. In a modern roundabout, entering traffic yields to traffic already circulating, at low speed. US studies of intersections converted from signals or stop signs show injury crashes down 72-80% and all crashes down 35-47%; at high-speed rural stop-controlled sites, injury crashes fell 85%.²⁰⁵ The Insurance Institute for Highway Safety (IIHS) estimates that converting 10% of US signalized intersections would have prevented 289 fatal crashes in 2024.²⁰⁵ The first modern US roundabouts were built in Nevada in 1990.²⁰⁵

The gains are not automatic. Two-lane roundabouts show smaller reductions and sometimes increases at first; in Washington State, crashes at two-lane roundabouts fell about 9% per year as drivers got used to them. Drivers failed to yield to pedestrians two to three times more often at multilane roundabouts than at single-lane ones.²⁰⁵ The safety gain comes from low speed and from removing right-angle and head-on left-turn collisions.

An FHWA safety team handout counts 32 vehicle conflict points at a four-way signalized intersection and 8 at a roundabout, which it describes as 75% fewer.²⁰⁶

Red light cameras: what the evidence says and who disputes it

Red light cameras photograph vehicles entering an intersection after the light has turned red, for ticketing. According to IIHS, 1,119 people were killed in red-light-running crashes in the US in 2024, about half of them pedestrians, cyclists or people in other vehicles.²⁰⁷

The research IIHS summarizes points toward fewer serious crashes, with a trade-off:²⁰⁷

• Large US cities with cameras had a 21% lower fatal red-light-running crash rate and a 14% lower rate of all fatal crashes at signalized intersections (Hu and Cicchino, 2017). In 14 cities that turned cameras off between 2010 and 2014, fatal red-light-running crash rates were 30% higher than expected.
• A seven-city FHWA-sponsored study found right-angle crashes fell 25% while rear-end crashes rose 15%; it judged the net economic effect positive because rear-end crashes tend to be less severe.
• A Campbell Collaboration review of 38 studies (Cohn and others, 2020) estimated 20% fewer injury crashes and 29% fewer right-angle injury crashes; a 2025 update by Hu and Cicchino gave 19%.

The number of US communities with camera programs has fallen since 2012, to 351 in 2025.²⁰⁷ IIHS is funded by insurers and supports camera enforcement. Opponents argue that longer yellow times achieve similar safety gains and that some programs are run for revenue. We have not reviewed their studies here, so we report the argument without weighing it.

An earlier federal study gives a more mixed picture. A 2005 FHWA evaluation of 132 camera sites in seven US jurisdictions found right-angle crashes fell 24.6% while rear-end crashes rose 14.9%, and concluded the cameras gave "a modest aggregate crash-cost benefit" of about $39,000 to $50,000 per site per year.²⁰⁸

Inside the traffic management center

Many cities run their signals from a traffic management center (TMC), a control room with camera feeds where engineers watch traffic, adjust timing and push plans out to the field. Central systems talk to field equipment using NTCIP (National Transportation Communications for ITS Protocol), a family of standards developed since 1996 by the Institute of Transportation Engineers (ITE), AASHTO and NEMA with the US Department of Transportation. NTCIP 1202 defines how a central station controls and monitors actuated signal controllers and their detectors.²⁰⁹

When the link to the center fails, a signal does not go dark; it keeps running its own local timing. A Boston traffic engineer described what that means: "it's basically running free, out of sync with the rest of the signals in that corridor".⁴⁷

In Boston

The Boston Transportation Department (BTD) runs the city's signals from its Traffic Management Center on the seventh floor of City Hall.⁴⁷ In fiscal year 2016, BTD operated 854 signals, 557 of them (about 65%) connected to the center, with about 87% online on average. Engineers built timing plans in Synchro software.²¹⁰ By 2020 the city had "almost 900 traffic signals", 699 on the central computer system, more than 300 BTD cameras and access to about 500 more from police and MassDOT.⁴⁷ State agencies also run signals on their own roads inside the city, so BTD's count does not cover every signal in Boston.

GBH's 2020 look inside the room described two to three engineers watching during rush hours, four default time-of-day plans (morning, off-peak, evening and overnight), a detailed survey of each signal every five years, and many signals flashing overnight.⁴⁷ An adaptive test was then planned for 47 signals in the Seaport.⁴⁷

A January 2018 Boston 25 News report said the state was seeking about $5 million to test the system, which could cover as many as 39 intersections.²¹¹ The city's Smart Streets page, last updated in October 2025, listed the Seaport adaptive signals network, planned with MassDOT, as "in design," with no intersection count.²¹² We did not find a report that it has gone live.

Newer layers include the MBTA bus priority pilot on Brighton Avenue⁹⁴ and Google's Project Green Light, which had expanded to 114 Boston intersections by May 2025.²¹³

What's changing now (2026)

Three changes are reshaping US signals, all incremental.

A new rulebook. The MUTCD (Manual on Uniform Traffic Control Devices), the federal rulebook for signals, signs and markings, was reissued as the 11th edition with a final rule published December 19, 2023 and effective January 18, 2024. States had until January 18, 2026 to adopt it, and Revision 1 was published and took effect March 5, 2026.²¹⁴

Signals that talk to cars. USDOT's National V2X Deployment Plan, released in August 2024, set a short-term goal of vehicle-to-everything (V2X) radios at 25% of signalized intersections in the 75 largest metro areas by 2028, and nationwide deployment in the 5.895-5.925 GHz band by 2036, according to trade press coverage.⁹⁸ The key message is SPaT (signal phase and timing), which tells a connected vehicle which light is showing and when it will change. NTCIP 1202 version 4, which ITE listed as still in balloting when we checked in October 2026, adds support for passing that timing data from controllers to roadside radios, including new concepts such as an "Assured Green Period", along with stronger network security.²⁰⁹

AI-suggested timing. Google's Project Green Light, launched in 2023, was active in 18 cities on four continents by May 2025. It uses AI and Google Maps driving trends to recommend timing changes, which city engineers can apply "in as little as five minutes". Google reports early results of up to 30% fewer stops and up to 10% lower emissions at intersections, as global figures.²¹³ These are company-reported, best-case numbers; we found no independent evaluation. The system advises human engineers rather than running signals itself.

How traffic lights differ around the world

Red for stop and green for go are near universal; the details are not.

• Britain shows red and amber together before green. In the UK Highway Code, "RED AND AMBER also means 'Stop'": do not move off until green. Amber alone means stop at the line unless you are too close to stop safely.²¹⁵ US signals go straight from red to green.
• Japan uses a deliberately bluish green. Old Japanese used the word ao for both blue and green, and the go light is officially ao. The commonly reported account is that in 1973 the government decreed the bluest shade of green allowed, so the lights still read as "go" internationally.²¹⁶ Japan, like the US, has not signed the 1968 Vienna Convention on Road Signs and Signals.²¹⁶
• Berlin kept East Germany's walking man. The Ampelmännchen was designed by traffic psychologist Karl Peglau on a 1961 commission from the East German transport ministry and debuted in East Berlin in 1969. After reunification, officials planned to replace it; a "Committee to Save the Ampelmännchen" won the right to keep it in 1997, and it has been a registered trademark since then.²¹⁷
• Turning on red is far more common in the US than in much of Europe, as described above; New York City is the large US exception.²⁰²

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10How the subway and the bus actually run

The short version: A subway is a set of electric trains drawing direct current from a rail or a wire, kept apart by a signal system, and watched from a control room. Buses run on schedules that agencies publish as open data, and live location feeds let your phone predict when the next one will arrive. Fares have moved from coins and cards to tapping a bank card or phone. Boston, which opened the first subway in the United States in 1897, spent 2023 and 2024 digging out from years of deferred maintenance and in 2026 is replacing its signals, its cars and its bus map.

How it changed: from horsecars to electric streetcars

Big-city transit became practical when streetcars went electric. Frank Sprague's Richmond Union Passenger Railway in Richmond, Virginia began carrying passengers on February 2, 1888.²¹⁸ The IEEE treats Richmond as the lasting prototype for electric street railways: it was more than three times larger than the average earlier electric line and ran more than eight times as many cars.²¹⁹ The idea spread fast. By 1895 nearly 900 electric street railways had been built in the US, and animal-powered railways had nearly disappeared within about a decade.²¹⁹

Sprague's second big contribution mattered more for subways. He invented multiple-unit control, which lets one operator run the motors in every car of a train at once, so a train can be any length without a locomotive at the front. Chicago's South Side Elevated placed the first order, followed by Brooklyn and Boston.²¹⁸ (He also built early electric elevators and sold that company to Otis in 1895.²¹⁸)

London's Metropolitan Railway, the world's first rapid transit line, opened in 1863 using steam locomotives; the first electric, fully underground line, the City & South London Railway, followed in 1890.²²⁰ Budapest and Glasgow opened subways in 1896 (Glasgow's ran by cable before it was electrified), Paris in 1900 and Tokyo in 1927.²²¹

Boston's builders said openly that they were following London, Glasgow and Budapest. Their design combined the "tube" style of construction pioneered in London with the open-excavation method used in Paris.⁸⁰ New York opened nearly nine miles of subway in October 1904, seven years after Boston.⁸⁰

Why Boston went underground first in the US

The subway was a cure for streetcar traffic, not a replacement for streetcars. Streetcar blockades choked downtown Boston in the 1890s, worst from Scollay Square down Tremont Street to Boylston Street.²²² Boston's council had approved a large electrification project after visiting Richmond in 1888,²¹⁹ and electrification made underground streetcar routes feasible, since electric cars, unlike steam engines, do not fill a tunnel with smoke. The 1892 Rapid Transit Commission studied them.²²²

The Boston Transit Commission began construction in 1895, and Boylston Street and Park Street stations opened on the morning of September 1, 1897.²²² The first train ran at 6 a.m., and more than 100,000 people rode it on opening day. It was built cut-and-cover: dig a trench down the street, build the box, roof it over. The legislature appropriated $5,000,000 and the project came in under budget.⁸⁰ That 1897 tunnel still carries the Green Line, which is why the Green Line is, mechanically, a streetcar line.

Two small disputes are worth flagging. Sources disagree on who built it: Mass Moments says the Boston Elevated Railway Company "built and operated" the subway, while the Leventhal Center credits the Boston Transit Commission with building it.⁸⁰²²² "Publicly planned, privately operated" is a fair summary until the record is checked. And "first in the US" has a challenger: reader comments on Mass Moments raise New York's 1869 Beach Pneumatic Transit, a roughly 300-foot demonstration line.⁸⁰

Did GM kill the streetcar?

A real conviction sits under a much bigger popular story. In 1949 a federal jury convicted General Motors, Firestone, Standard Oil of California, Phillips Petroleum and Mack Trucks of conspiring under the Sherman Antitrust Act to monopolize the sale of buses and supplies to transit companies controlled by National City Lines (NCL). The same jury acquitted them of conspiring to monopolize ownership of those transit companies.²²³ GM was fined $5,000, and its treasurer was fined $1. The verdicts were upheld on appeal in 1951.²²³

By 1947 NCL owned or controlled 46 systems in 45 cities, and the historian Robert Post estimated the alleged conspiracy reached only about 10% of US transit systems.²²³ Bradford Snell's 1974 Senate testimony popularized the bigger story. Most scholars instead point to a long list: overcapitalization, fixed fares during inflation, the Depression, the Public Utility Holding Company Act of 1935, labor unrest, congestion, sprawl, highway and tax policy, and plain consumer preference for cars.²²³

Third rail or overhead wire: how trains get power

Subway and streetcar trains run on direct current (DC). A traction power substation converts grid power (see How electricity gets to your building) into that current and feeds it to the track. The train picks it up one of two ways:

• Third rail: a powered rail beside the running rails, touched by a sliding shoe on the train. It is compact and suits tunnels, but a live rail at ground level is a hazard anywhere people can reach it.
• Overhead catenary: a wire strung above the track, touched by a pantograph or trolley pole on the roof. Keeping the power out of reach is why lines that run in the street, among people and cars, use it.

In Boston, all four rail lines run on 600 volts DC. The Red and Orange Lines use third rail. The Green Line uses overhead catenary. The Blue Line does both: third rail from Bowdoin to Airport, then overhead wire from Airport to Wonderland along the shore, and a state document says its cars are the only ones in the US equipped for both.⁵¹ Feeding all that takes 48 traction power substations, 10 power substations, 67 unit substations and 3 switching stations.⁵¹ The same network powers tunnel lighting and ventilation fans.⁵¹

Tunnels also take on water constantly, from below. New York's subway has 300 underground pump rooms. Groundwater seeps in all the time, storms add more through vent gratings, stairs and manholes, and the water collects in sumps until pumps switch on at a set level. On a normal day they remove about 13 million gallons, and roughly double that in heavy rain.⁵²

How do subway signals keep trains apart?

A train cannot stop the way a car can: steel wheels on steel rail take a long distance to brake, so the operator's eyes cannot be the only protection. Signals do that job.

The classic method is the fixed block: the track is divided into sections, and only one train may be in a section at a time. A track circuit, a low current running through the rails, detects a train because its wheels and axles short the circuit. Signals at the entrance to each block show whether it is clear. A trip stop is a trackside device that stops a train automatically if it runs a red signal.

Boston has nearly every generation of this technology at once:⁵¹

Cab signaling moves the speed command into the train, which makes it harder to miss on a curve or in fog. The Green Line is the gap: on the surface it runs on operating rules, so the operator is the protection. A Green Line Train Protection project is adding fail-safe protection,⁵¹ recommended after a derailment that injured seven people.²²⁴

Headway, the time between one train and the next, is set mostly by the signal system. Fixed blocks force every train to stay at least a whole block behind the one ahead, however short the real braking distance is. Newer communications-based train control (CBTC) tracks each train's exact position by radio, so the safe gap can shrink and move with the train.

New York's MTA describes CBTC as using wireless links to keep trains in constant contact with a central system. Fixed-block signals only know that a train is somewhere in a section that can be over 1,000 feet long; CBTC knows exactly where each train is, so the protected space moves with the train. As of 2025 it runs on the L line (installed 2009) and the 7 line (2019), with more lines under construction.²²⁵

Automation is graded under the IEC 62290 scale from GoA0 (on-sight, no automation) through GoA2 (automatic starting and stopping, with a driver in the cab) to GoA4, where starting, stopping and doors are fully automated with no staff needed on board.²²⁶

Who is in the operations control center?

An operations control center (OCC) is the room where dispatchers watch train positions, give orders to operators, hold trains, call for shuttle buses and coordinate with police and fire. It is where a broken-down train becomes a planned diversion instead of a line of stranded trains.

That room got federal attention in Boston. After a string of derailments, collisions and injuries, the Federal Transit Administration (FTA) ran a Safety Management Inspection of the MBTA starting in mid-April 2022, lasting two and a half months.²²⁷ Its central finding, released at the end of August 2022, was that the T had shifted attention and resources from operations and maintenance to capital projects, and that services were not adequately staffed, trained, supervised or maintained.²²⁸

Ten special directives followed, eight to the MBTA and two to the state's safety overseer, the Department of Public Utilities (DPU). They included SD 22-4 on track maintenance, SD 22-5 on securing disabled trains, SD 22-6 on the operations control center and SD 22-9 on workforce.²²⁷ The DPU was told to improve its own oversight capacity.²²⁹ A 2026 amendment modified the directives still open.²²⁷

The American Public Transportation Association's standard for operations control centers (revised January 2025) calls the OCC "the main location from which all aspects of the system are controlled." At larger agencies it tracks every train in real time along with switches, signals, interlockings and traction power, on wall panels or console displays, and controllers can operate switches and wayside signals remotely.²³⁰ Typical positions include an OCC manager, train controllers or dispatchers who direct train movements and start emergency procedures, a traction power supervisor, a communications console operator and a police or security dispatcher, and the standard calls for minimum staffing on every shift.²³⁰

Fares: from tokens to tap-to-ride

The broad arc runs from coins and tokens, to magnetic-stripe cards, to agency smartcards that store value, and now to open-loop payment, where riders tap the bank card or phone they already carry instead of a card the agency issues.

Hong Kong's Octopus, a contactless smartcard shared by the main transport operators, launched in September 1997.²³¹ London introduced Oyster pay-as-you-go on June 30, 2003, accepted contactless bank cards on buses from December 13, 2012, and extended them to the Tube, London Overground and National Rail on September 16, 2014.²³² New York's OMNY took its first taps on May 31, 2019, on the 4, 5 and 6 lines between Grand Central and Atlantic Avenue and on Staten Island buses, the start of replacing a MetroCard system that had served the city for over 25 years.²³³

In Boston, contactless payment went live in early August 2024 on buses and on Green Line and Mattapan trolleys, with the older CharlieCard readers left in place beside the new screens.²³⁴ The MBTA had announced an August 1 start.²³⁵ The trade press framed it as catching up with New York, Denver, Chicago, Baltimore and San Francisco.²³⁴ The launch article names buses and trolleys only, so we do not claim the heavy-rail subway gates took taps on day one.²³⁴

It has not been cheap. The 2017 fare contract with Cubic Transportation Systems was $723.3 million, and after amendments it was expected to cost about $935.4 million. Commuter Rail contactless was planned for spring 2026.²³⁴ Enforcement changed too: in 2025 the T began fining Green Line fare evaders up to $150.²²⁴

The opposite approach is also running in Boston. The city funds fare-free service on bus Routes 23, 28 and 29. The pilot began on Route 28 in 2021, expanded to the other two in March 2022, and is extended through December 2026 with $8 million in federal pandemic-relief (ARPA) money. The three routes carry nearly 23,000 weekday trips, and all-door boarding cut the time buses spend stopped at each stop by about 20%.²³⁶

How does the app know where the bus is?

Most transit apps, from Google Maps to small local ones, read the same two open data formats.

• GTFS (General Transit Feed Specification) is a set of plain files an agency publishes: routes, stops, trips and schedules.
• GTFS-Realtime is a companion live feed: delays, vehicle positions and service alerts.

GTFS began in Portland, Oregon. TriMet IT manager Bibiana McHugh and Google engineer Chris Harrelson led the effort, and Google Transit launched with Portland's data on December 7, 2005.⁸⁸ In September 2006 five more US cities were added and the format was released as the "Google" Transit Feed Specification; a rename to "General" was proposed in 2009.²³⁷ The MBTA was one of the agencies, with TriMet, BART and San Diego MTS, that worked with Google on the real-time extension.⁸⁸ Today the Transitland project collects GTFS and GTFS-Realtime feeds from more than 55 countries.²³⁷

The chain from bus to phone goes like this. A GPS unit on the bus (automatic vehicle location) reports its position to the agency. The agency publishes those positions, and its predicted arrival times, as a GTFS-Realtime feed. Your app matches the live position against the static schedule to work out which trip the bus is running and when it should reach your stop. Independent trackers are built on live agency data in the same way; one is Charlie, an MBTA tracker from the publisher of this guide.

Buses: the redesign and the fight for curb time

Much bus delay comes from time spent stopped: at red lights, in traffic and at stops while people board one at a time. Bus lanes, signal priority and all-door boarding all go after that same lost time. Boston's fare-free routes give one measured result: the 20% dwell-time cut noted above.²³⁶

The model for modern bus rapid transit (BRT) came from Curitiba, Brazil, whose first busways opened in 1974; the system later added raised tube stations where riders pay before boarding and step onto the bus at platform level.²³⁸²³⁹ Bogota's TransMilenio began operating in late 2000 with two main corridors, running articulated buses on dedicated lanes.²³⁹

In Boston, the Bus Network Redesign redraws the map around frequency. Phase 1 launched December 15, 2024, with Frequent Routes 104, 109 (new), 110 and a combined 116. A Frequent Route comes every 15 minutes or better all day, and the frequent network is set to double from 15 to 30 routes once all phases are complete.²⁴⁰

In Boston: slow zones and the long dig-out

A slow zone, or speed restriction, is a stretch where trains must slow down because the track or what holds it up is in poor condition. By 2023 they were everywhere. In June 2023, speed restrictions covered 21.8% of subway track.²⁴¹ On September 5, 2023 the count stood at 115 on the Red Line, 65 on the Green, 38 on the Orange and 15 on the Blue, 233 in all.²⁴²

Under General Manager Phil Eng, the Track Improvement Program used planned partial shutdowns to replace and repair track. By December 2, 2024 only two slow zones remained, both on the Green Line between Government Center and North Station, and the Red and Orange Lines were already clear.²⁴³ On December 23, 2024 the last one was removed. Officials called it the first commute in two decades without a slow zone, and Gov. Healey said the restrictions had cost "nearly a million dollars every day in GDP." That same day a cracked rail near Wollaston forced shuttle buses.⁹²

The gains held in measurable ways. In 2025 the Orange Line reached its 55 mph limit and the Red Line reached 50 mph for the first time in decades. Lines still shut for track work that year, and ceiling tiles fell at Harvard and Park Street.²²⁴ Restrictions also come back as defects turn up: one between Savin Hill and Fields Corner on the Red Line, in place since August 2025, had been lifted by late May 2026.²⁴⁴ Our reading is that "largely free of slow zones, with occasional temporary restrictions" describes 2026 better than "zero."

The Green Line Extension (GLX) pushed the Green Line 4.3 miles into Somerville and Medford with seven stations. The Union Square Branch opened March 21, 2022 and the Medford Branch December 12, 2022. It cost $2.28 billion, about $1 billion of it federal. It also had a construction defect: track laid too narrow, the wrong gauge, led to speed restrictions as low as 3 mph in 2023 and regauging late that year.²⁴⁵

New cars came from CRRC, a Chinese manufacturer, with final assembly in Springfield, Massachusetts.²⁴⁶ The Orange Line order of 152 cars was nearly done by November 20, 2025, with 150 delivered and the last two due that December; the new cars have run since 2022.²⁴⁶

The Red Line order is far behind. Of 252 cars, 58 had arrived by November 2025. US Customs and Border Protection held car shells from May 2025 to review compliance with the Uyghur Forced Labor Prevention Act. The contract dates to 2014, and a 2024 "reset" pushed its value above $1 billion with a late-2027 deadline.²⁴⁶ Sixty cars had been delivered by late January 2026, and CBP released the shells in March 2026 after nearly 10 months, leaving the 2027 target in doubt.²⁴⁷

What's changing now (2026)

• Red Line signals: a digital signal system is replacing analog signals. It was 70% complete in May 2026, with completion expected toward the end of the year.²⁴⁴
• Red Line cars: shells released in March 2026; whether the full fleet arrives by late 2027 is an open question.²⁴⁷
• Green Line safety: the Train Protection System is being built to stop collisions on the surface sections.⁵¹
• Fares: Commuter Rail contactless was planned for spring 2026,²³⁴ and the fare-free bus pilot runs through December 2026.²³⁶
• Federal oversight: FTA amended the remaining open special directives in 2026.²²⁷

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11Roads, bridges, tunnels and the hole in your street

The short version: A road is a layered structure, and potholes start when water gets under the top layer and freezing and traffic finish the job. In the US, bridges have been inspected under federal standards since 1971, today usually every two years, and graded good, fair or poor by their weakest part. Before anyone digs in a US street, call-before-you-dig rules have utilities mark what is buried there, and many cities restrict digging in freshly paved streets. Boston carries the scars and lessons of the Big Dig, whose tunnel ceiling collapse in 2006 killed a driver, and is trying to reach zero traffic deaths by 2030.

What is under the asphalt?

A street looks like one slab, but it is a stack. In the language of pavement engineers, an asphalt road is a flexible pavement: a bound surface layer sitting on a base course of angular crushed rock, which sits on the subgrade, the native soil the road is built on.⁷⁵ The surface keeps water out and gives tires grip, and the base spreads each wheel load over a wider area so the soil underneath is not overloaded. Angular rock is used because sharp-edged stones interlock where round ones would roll.

That division of labor explains most road failures. As long as the surface stays sealed, the base and soil stay dry and strong. Once water gets through, the whole stack starts to fail from below.

Why are potholes worse in spring?

Potholes form in a sequence.⁷⁵

1. Cracks. The surface ages and cracks under traffic and weather.
2. Water gets in. Rain and snowmelt seep through the cracks into the base and subgrade, and the soil softens.
3. Pumping. Each passing tire pushes down on the wet layer and squeezes water, carrying fine soil particles with it, out through the cracks. The support under the surface thins out.
4. Feedback. Less support means more flexing, more flexing means more cracks, and more cracks let in more water, until the surface breaks away.

Cold climates add a sharper tool. "Water expands when it freezes, and it does so with tremendous force." Thin layers of water between pavement and base freeze and grow into formations called ice lenses, which lift the pavement. "When those lenses thaw out, all the ice that was supporting the pavement goes away, creating voids."⁷⁵ The surface is then bridging over empty space, and traffic breaks it. That is why potholes are worst during the spring thaw.⁷⁵ A freeze-thaw cycle is one round of that freezing and melting. So a winter that swings above and below freezing many times can do more damage than one that stays steadily cold.

Minnesota DOT research at its Mn/ROAD test road found that during a partial thaw, pavement layers can sit "in a saturated, weakened state" from trapped water, and that the stiffness of the aggregate base drops sharply just after the thaw passes through it.²⁴⁸ In Boston, at a May 8, 2026 City Council hearing, Chief of Streets Nick Gove said the average pothole case was resolved in 18 hours and over two-thirds within 24 hours; figures shown at the hearing counted over 4,000 pothole-repair requests in East Boston over five years.²⁴⁹

This also explains why a cold patch put down in March can fail by May. A cold patch is a temporary repair: it plugs the hole in the surface but cannot fix the wet, weakened layers underneath.

How it changed: why US bridges get inspected

US bridge inspection is a federal system built up over decades:

The trigger was the Silver Bridge, which carried US 35 over the Ohio River between Point Pleasant, West Virginia, and Gallipolis, Ohio. It collapsed on December 15, 1967, killing 46 people; the cause was the sudden fracture of a single eyebar in a suspension chain, starting from a defect about 0.1 inch (2.5 mm) deep.²⁵³ Congress responded with a bridge inspection section in the Federal-Aid Highway Act of 1968, and the National Bridge Inspection Standards followed on April 27, 1971.²⁵³

How often are bridges inspected?

Under the current US rule, the baseline is a routine inspection every 24 months. A bridge in good shape that meets set criteria can go up to 48 months. A bridge with a relevant component rated 3 ("serious") or lower on a 0-to-9 scale gets inspected every 12 months.²⁵¹

Inspectors rate each major part of a bridge separately: the deck (the surface you drive on), the superstructure (the beams or girders that hold up the deck), the substructure (piers, abutments and foundations) or, for a buried pipe-like crossing, the culvert. The bridge's overall condition is set by the lowest of those ratings:²⁵²

These definitions come from the January 2017 Pavement and Bridge Condition Performance Measures rule.²⁵² A "poor" rating does not mean "about to fall down": it means at least one major part has deteriorated badly enough to need serious attention, and the 12-month interval for low ratings is how the system watches those bridges more closely. Older news stories use the term "structurally deficient." How exactly that older label maps onto "poor," and when federal reporting switched, is not confirmed by our sources.

The US also has a separate federal program for road tunnels, the National Tunnel Inspection Standards, published in the Federal Register on July 14, 2015.²⁵⁴²⁵⁵

In Boston: the Big Dig ceiling collapse

The Big Dig is the common name for Boston's downtown highway and tunnel megaproject, which includes the I-90 connector tunnel.²⁵⁶

It replaced the deteriorating six-lane elevated Central Artery (I-93) with an underground expressway, built a four-lane tunnel under Boston Harbor and added the Leonard P. Zakim Bunker Hill Memorial Bridge. Construction ran from 1991 to 2007, and FHWA puts the cost at $14.8 billion, $7 billion of it federal.²⁵⁷ Other accounts give $14.6 billion at completion in December 2007, and about $21.9 billion once interest is counted.²⁵⁸

On July 10, 2006, about 12 tons of concrete ceiling panels fell in the I-90 connector tunnel, killing Milena Del Valle, 39. Each panel weighed 4,600 pounds (about 2,090 kg), and the anchors holding the ceiling up were set with epoxy adhesive.²⁵⁶

The National Transportation Safety Board named the likely cause as the "use of an epoxy anchor adhesive with poor creep resistance."²⁵⁶ Creep is slow deformation of a material under a constant load. The epoxy did not snap; under constant load it gave way a little at a time, and the anchors slowly pulled out until the panels fell. The fast-set epoxy was supplied by Powers Fasteners and installed by Modern Continental.²⁵⁶

The lesson is about load that never lets up. A ceiling panel puts the same weight on its anchors every second of every day, so a material that holds in a short test can still fail over a long time. The MBTA's 2025 fallen ceiling tiles at Harvard and Park Street stations, covered in How the subway and the bus actually run, are a reminder that overhead hazards are not only a highway problem.²²⁴

Tunnels also need light and air. In Boston, the MBTA's power network feeds tunnel lighting and ventilation fans.⁵¹ How highway tunnel ventilation is engineered is beyond what our sources for this section cover.

Why do they keep digging up the same street?

Under a city street sit water mains, sewers, gas lines, and electric and telecom conduits, owned by a mix of public agencies and private companies. Each owner has to dig to fix or replace its own lines, often on its own schedule. (The cables and conduits get their own tour in 311, the wires under the street, and city data.) Two rules try to keep that from wrecking the street and the people digging.

Call before you dig. In Massachusetts, anyone excavating - a utility crew, a contractor or a homeowner setting a fence post - must first premark the area with white paint or stakes, then notify Dig Safe at least 72 business hours ahead. Weekends and holidays do not count. The national call-before-you-dig number, 811, reaches it. Dig Safe is a nonprofit, and it tells the utilities with lines in the area to come and mark them. A ticket is valid for 30 days.⁶⁸

The paint and flags you see on sidewalks are this process made visible: the white premark answers "where will we dig?" and the utilities' marks answer "what is down there?"

Protect new pavement. Many cities restrict digging in streets they have recently rebuilt. In Cambridge, Massachusetts, a street rebuilt or resurfaced within the past five years is a "Moratorium Street" and may not be dug up except in an emergency or with the Commissioner's approval. Every street-opening permit needs a Dig Safe number.⁶⁹ The rules also govern how the hole is closed: the backfill has to be compacted to 95% of a lab standard called modified Proctor density, so the trench does not settle into a dip, and if patches end up less than 10 feet (about 3 meters) apart, the permit holder must mill and repave the street curb to curb.⁶⁹

Moratoriums also work as a coordination tool. A utility that knows a street is about to be repaved has every reason to replace its pipes first, because afterward the street is closed to it for years. Cities use their paving schedules to pull water, gas and electric work into the same window.

In Boston, utilities are expected to finish first: before a street is resurfaced, each utility completes its work and signs off on the block in the City of Boston Utility Coordination Software (COBUCS), the city's reservation system.²⁵⁹

What is Vision Zero?

Vision Zero is a road-safety policy that sets the goal of eliminating all traffic deaths and serious injuries.

The idea comes from Sweden, where Parliament decided by a large majority in autumn 1997 to make Vision Zero the basis of national road safety work.²⁶⁰ In the US, Hoboken, New Jersey, became a Vision Zero city by executive order in 2019. In January 2024 the city reported seven consecutive years without a traffic death and listed measures such as daylighting delineators at 31% of intersections, curb extensions and a 15 mph school-zone limit on 67 blocks.²⁶¹

In Boston, the city joined Vision Zero in 2015 under Mayor Walsh, with a target of zero traffic deaths by 2030. A resolution filed with the City Council on July 22, 2026, recommitting to that goal, cites 11 traffic deaths in 2025, most of them pedestrians. The tools it lists include a lower default speed limit, Neighborhood Slow Streets and a 2023 update to the city's action plan.²⁶²

In our reading, what the policy changes in practice is the default question after a crash: what about the street, and the speed it invited, allowed it to happen, alongside who was at fault. Specific measures such as speed limits and street redesigns are argued over locally, and this guide does not take a side.

What's changing now (2026)

• Bridge inspection: the updated NBIS rule, in effect since June 2022, is the standard states now inspect to, with risk-based intervals from 12 to 48 months.²⁵¹ FHWA last updated its national bridge condition tables in September 2026.²⁵²
• Boston Vision Zero: a resolution recommitting the city to the goal was filed with the City Council in July 2026, with four years left before the 2030 target.²⁶²
• Digging: Massachusetts' 72-business-hour Dig Safe notice and Cambridge's five-year moratorium remain the working rules.⁶⁸⁶⁹

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12Where your trash actually goes

The short version: In the US, about half of everyday trash goes into engineered landfills, about a third is recycled or composted, and about an eighth is burned to make energy, according to the most recent federal figures (2018). Where your bag ends up depends on your city's contracts: Boston burns most of its residential trash, Copenhagen burns its trash under a ski slope, and South Korea weighs its food scraps. Recycling captures far less than it could (one national estimate is 21% of US residential recyclables), and China's 2018 import ban exposed how much of it depended on shipping bales overseas. Collecting all of it is one of the five deadliest jobs in the US.

How much trash does one person make?

The US Environmental Protection Agency (EPA) counts municipal solid waste (MSW): the everyday trash from homes, schools, offices and shops, as opposed to industrial or hazardous waste. In 2018, the latest year EPA has published, the US generated 292.4 million tons of it, or 4.9 pounds (2.2 kg) per person per day.²⁶³ EPA changed how it measures food waste between 2017 and 2018, so those two years are not directly comparable, and as of the page's December 2025 update there was still no newer national year.²⁶³

Where it went in 2018:²⁶³

Those are national averages. A single city can look very different, as Boston does.

How it changed: from pigs to parks

Before cities collected garbage, something else ate it. Around 1820, about 20,000 pigs roamed New York, roughly one for every five residents, according to historian Catherine McNeur.²⁶⁴ They ate nearly any organic waste and were owned mostly by poor New Yorkers and butchers.²⁶⁴ When the city tried to round them up, people who depended on them fought back: "pro-hoggites" rioted against pig-collection officers in 1821, 1825, 1826 and 1832.²⁶⁴ Only after the 1849 cholera epidemic did the city remove the pigs, corralling 5,000 to 6,000 by June of that year; much of the waste they had eaten then went into the Hudson River instead.²⁶⁴

Horses were the bigger mess. In the 1890s, New York's horses left an estimated 2.5 million pounds (about 1,100 tonnes) of manure and 60,000 gallons (227,000 liters) of urine on the streets every day; dead horses were left where they fell, and garbage piled a foot or two deep.²⁶⁵

A popular story says this all came to a head in the "Great Horse Manure Crisis of 1894," with a Times of London writer predicting nine feet of manure on London streets and an 1898 planning conference collapsing in despair. That story does not hold up. The quote has never been found, the newspaper refuted the attribution in 2018, and the earliest known telling is a September 2004 article by Stephen Davies for the Foundation for Economic Education's magazine The Freeman.²⁶⁶ There is no record of the supposed conference outcome either.²⁶⁶ The real part is that manure changed from a product people sold into a disposal problem; an 1893 London complaint described exactly that shift.²⁶⁶

The turn toward a professional sanitation service came in 1895, when New York brought in sanitary engineer George E. Waring Jr.²⁶⁵ His first move was a law requiring horses and carts to be stabled overnight instead of left in the street.²⁶⁵ His Street Cleaning Department workers wore white uniforms and pith helmets and pushed wheeled carts. Carcasses were sold for glue, manure for fertilizer, and other refuse went to waterfront dumps; a parade honored the department in 1896.²⁶⁵ Waring died on October 29, 1898, of yellow fever he caught while studying sanitation in Cuba.²⁶⁵ His model, a disciplined, uniformed, salaried public workforce, looks a lot like today's city sanitation departments (more in Keeping streets clean and open).

The uniforms gave Waring's sweepers their nickname, the "White Wings."²⁶⁷

In the 20th century, New York burned and buried. Its municipal incinerators peaked at 21 plants in 1937; only ten were running by 1946.²⁶⁸ In April 1948 the first garbage scow arrived at Fresh Kills on Staten Island, a landfill meant to be temporary.²⁶⁸ It grew to 2,200 acres (890 hectares), took about 29,000 tons a day at its 1986-87 peak, and received its last barge on March 22, 2001, after a 1996 state law ordered it closed.²⁶⁸

It reopened briefly after September 11, 2001, to sort about 1.6 million tons of World Trade Center debris.²⁶⁸ Reclamation into Freshkills Park, about three times the size of Central Park, began in October 2008 as a 30-year phased project; the first section, Schmul Park, opened in 2012.²⁶⁸

How does a modern landfill work?

A sanitary landfill is the opposite of an open dump: waste is compacted and covered rather than left exposed. In the US, federal rules for municipal landfills come from Subtitle D of the Resource Conservation and Recovery Act (RCRA), written up in 40 CFR part 258.²⁶⁹ The main parts:²⁶⁹

• Composite liner: a flexible plastic sheet (a geomembrane) laid over two feet (60 cm) of compacted clay, forming the bottom of each cell.
• Leachate collection: a drainage and removal system on top of the liner that catches leachate, the liquid that seeps down through buried garbage.
• Daily cover: waste is compacted and frequently covered with several inches of soil.
• Groundwater monitoring: operators test wells around the site.
• The long tail: the rules also cover where a landfill can be sited, how it is closed, care after closure, cleanup if something leaks, and proof that the owner can pay for all of it.

EPA counted about 1,908 MSW landfills in the US in 2009.²⁶⁹

Buried trash makes gas. Once the oxygen in a landfill runs out, bacteria break down the organic waste and produce landfill gas, which is about half methane and most of the rest carbon dioxide.²⁷⁰ Landfills can capture it with vertical wells drilled into the waste and piped to a blower and flare or vacuum system, and the gas can be burned or used as fuel.²⁷⁰ EPA ranks municipal solid waste landfills as the third-largest source of human-related methane emissions in the US, about 14.4 percent of the total in 2022.²⁷⁰

Who picks up the trash?

There is no single model. Some cities use their own public crews; New York's Department of Sanitation (DSNY) collects residential trash. Others, like Boston, hire private contractors. In many US cities, business trash is a free market where each shop or restaurant picks its own hauler, which means several companies' trucks may run down the same block on the same night.

New York tried to fix that last part with Local Law 199 of 2019, which created commercial waste zones.²⁷¹ The city is divided into 20 zones; DSNY authorizes three private carters per zone, plus five carters citywide for large containers and compactors.²⁷¹ The stated goals are worker safety standards, better service, more recycling and composting, and fewer truck miles and emissions.²⁷¹ The first zone, Queens Central (Jackson Heights, Corona, Elmhurst and parts of Forest Hills and Ridgewood), began implementation in September 2024 and was fully implemented by January 2025, with about 150 notices of violation issued in its first three months.²⁷¹

In Boston, the Public Works Department does not manage commercial waste; businesses hire private haulers.⁶⁰

Most US collection uses rear loaders (a crew throws bags into a hopper), side loaders with a mechanical arm that grabs standard wheeled carts, or front loaders that lift dumpsters. Rear loaders have long been the standard for residential routes and usually need a crew of two or three, while front loaders are used mostly for commercial collection.²⁷² Automated side loaders, first introduced in Scottsdale, Arizona, in 1969, let one driver empty curbside carts without leaving the cab, and they are increasingly replacing rear loaders in US cities.²⁷³ Full trucks often do not drive straight to a landfill; many unload at a transfer station, where trash is consolidated into bigger trucks, rail cars or barges for the long haul.

EPA defines transfer stations as facilities where municipal solid waste is unloaded from collection vehicles, held briefly, and reloaded onto larger long-distance vehicles bound for landfills or other disposal sites.²⁷⁴

In Boston: the life of one trash bag

Boston generates about 250,000 tons of residential waste a year.⁶⁰ Here is what happens to one bag of it. The contract details are sourced; where we describe standard industry practice, we say so.

1. The curb. A resident in a three-decker sets the bag out on trash day.
2. The pickup. A crew from Capitol Waste Services, which holds the city's residential collection contract (three years from July 2024, with two optional years), lifts it into a packer truck that compacts it.⁶⁰
3. The haul. The truck takes the load to a waste-to-energy plant. Boston's disposal contracts are with Reworld (formerly Covanta) and WIN Waste Innovations (formerly Wheelabrator), both extended in 2024.⁶⁰
4. The furnace. A waste-to-energy plant burns trash in a controlled furnace and uses the heat to make steam, which drives a turbine for electricity. The bag does not go into a hole in the ground first.
5. What's left. Burning shrinks the volume a lot, but it leaves ash.

In Massachusetts, that ash must be buried in landfills specifically approved to take it; the state lists the Ward Hill Neck ash landfill for Reworld's Haverhill plant and the RESCO ash landfill for WIN Waste's Saugus plant.²⁷⁵ The Dorchester Reporter, in an undated article, traced Boston residential trash to the Haverhill incinerator and reported that magnets pull metals, including coins, out of the ash for recycling before the rest goes to a monofill, a landfill for one kind of waste.²⁷⁶

Most of Boston's collection and disposal contracts expire around June 2027, and in November 2024 the city issued a request for information (RFI) asking the industry about its next round, including route optimization, fleet electrification and containerization.⁶⁰ Because most of its residential trash is burned rather than buried, Boston sits closer to the Scandinavian model than the US average.

If the bag had been recycling instead, it would go to Casella Waste Systems' materials recovery facility in Boston, whose contract was extended three years in 2024; Casella spent about $20 million upgrading the plant.⁶⁰ If it were food scraps from a household in the city's curbside program, it would go to one of two contractors, Save That Stuff or Garbage to Garden.⁶⁰

The city's 2019 Zero Waste Plan set out 30 strategies and a target of 80% diversion from disposal by 2035, up from about 25%.²⁷⁷ At the time, the city said Boston generated about 1.2 million tons of materials a year (counting all sectors), 75% of which went to incinerators or landfills, and that 39% of what was thrown away as trash was recyclable and 36% compostable.²⁷⁷

Does recycling actually get recycled?

A common US setup is single-stream recycling: paper, cans, bottles and containers all go in one bin, and the sorting happens later at a materials recovery facility (MRF), which separates the mix into bales of paper, metal and plastic to sell. A MRF typically combines screens that bounce flat paper away from round containers, magnets for steel, eddy currents that push aluminum off the belt, optical sorters that read plastic types, and people picking items by hand.

The weak point is not mainly the MRF. A national study by The Recycling Partnership, reported in January 2024, estimated that only 21% of US residential recyclables are actually captured.²⁷⁸ The losses happen before the truck:²⁷⁸

• 73% of households have recycling access: 85% of single-family homes, but only 37% of multifamily buildings.
• 59% of households with access participate.
• MRFs capture about 87% of the recyclables they receive.

Contamination means items that should not be in the bin, or recyclables too dirty to sell, which lower the value of bales or jam machines.

The Recycling Partnership's 2020 State of Curbside Recycling report found that only about a third of US communities knew their contamination rate, and among those the average inbound contamination was 17 percent, as reported by Waste Today.²⁷⁹

What did China's National Sword do to recycling?

For years, many rich countries shipped mixed bales of paper and plastic to China. In 2017 China launched a policy called National Sword, and in 2018 it banned many recyclables, including plastics, and set a 0.5% contamination limit on the scrap it would still accept.²⁸⁰ A University at Buffalo study found that US plastic sent to landfill rose 23.2% afterward, and one facility it examined saw its operating costs double.²⁸⁰ Our reading: the ban did not create recycling's problems so much as reveal them, because a lot of material had been counted as "recycled" when it was baled and shipped, without much attention to what happened next.

Who pays for packaging? Extended producer responsibility

Under extended producer responsibility (EPR) for packaging, the companies that sell products in packaging pay for collecting and recycling it, usually through a nonprofit called a producer responsibility organization (PRO). As of 2026, seven US states have enacted packaging EPR laws: California, Colorado, Maine, Maryland, Minnesota, Oregon and Washington.²⁸¹ Maryland became the sixth on May 13, 2025 (SB 901), and Washington the seventh when its law was signed on May 17, 2025.²⁸²

Oregon was the first state to actually invoice producers and collect fees.²⁸³ One PRO, Circular Action Alliance, serves California, Oregon, Colorado, Minnesota and Maryland.²⁸³ As of December 2025, Hawaii, Rhode Island, Massachusetts, Illinois and Connecticut were conducting needs assessments, a common step before legislation.²⁸³

The idea is to move the cost of packaging from city budgets to the companies that choose the packaging, on the theory that whoever pays will design for less of it. The US programs are new enough that results are not yet in.

What about food scraps?

Food scraps are heavy, wet and a large share of household trash. Boston's own 2019 numbers put compostable material at 36% of its trash.²⁷⁷

South Korea took the most aggressive route. It banned landfilling food waste in 2005, and its food waste recycling rate rose from 2% in 1995 to 95%.²⁸⁴ Biodegradable bags have been used since 2013, and Seoul has about 6,000 RFID smart bins that weigh each resident's food scraps and charge them via an ID card.²⁸⁴

In Boston, the Curbside Food Waste Collection program began in 2022 with 10,000 households.²⁸⁵ As of September 2026 it had about 27,000 participants; it is free, open to buildings with six or fewer units, and has a waitlist, with more households being added in fall 2026.²⁸⁵ (A November 2024 report put participation at about 24,000 residents.⁶⁰) The city's 20 Project Oscar drop-off bins collected 223,446 pounds (about 101 tonnes) in 2025.²⁸⁵ Massachusetts requires businesses that produce more than half a ton of food waste per week to keep it out of the trash.²⁸⁵

Why does Scandinavia burn its trash?

Northern Europe and Japan burn much of their waste for heat and electricity instead of burying it.

Copenhagen. The Amager Bakke plant, better known as CopenHill, is owned by five municipalities through Amager Ressourcecenter. It burns about 400,000 tonnes of waste a year and supplies power and heat for 150,000 homes.⁶¹ It cost about EUR 470 million, was designed by the architecture firm BIG, finished construction around 2017, and opened a ski slope on its roof in October 2019.⁶¹

Sweden. As of a 2018 report, Sweden landfilled about 1% of its waste, ran more than 30 waste-to-energy plants, and imported about 1.3 million tonnes of waste a year, mostly from Norway and the UK, which made up 20-25% of the waste it burned in 2016.²⁸⁶ Sweden scrapped its incineration tax in 2010.²⁸⁶ The same report questioned whether the imports are as green as they look; the critique is that plants that need fuel create pressure to keep waste coming. These figures are several years old and current numbers likely differ.

Japan. Each municipality sets its own categories, usually burnable, nonburnable, recyclable and oversized, and many require designated bags of 5 to 40 liters.²⁸⁷ The town of Kamikatsu sorts into 45 types across 13 categories.²⁸⁷

South Korea. Designated garbage bags have been in use since 1995, and Seoul's RFID food waste bins (above) charge by weight.²⁸⁴ Both are versions of what is often called pay-as-you-throw: the more you discard, the more you pay.

The US middle ground is landfill-heavy: 11.8% of US MSW was burned with energy recovery in 2018.²⁶³

Can trash travel by tube?

A few places move trash through underground pipes instead of trucks. On New York's Roosevelt Island, a pneumatic waste system built by the Swedish company Envac opened on April 1, 1974.²⁸⁸ Envac installed its first system in 1961.²⁸⁸ Trash dropped down chutes in more than two dozen buildings travels at 60 to 70 mph (about 100 to 110 km/h) through 20-inch (51 cm) tubes to a central DSNY compactor, serving more than 14,000 residents.²⁸⁸ As of 2020 it was one of only two US systems at that scale (the other is at Walt Disney World), and it got a $1.7 million upgrade starting in 2019.²⁸⁸

A cheaper idea sits on the sidewalk. Bigbelly, founded in 2003 and based in Needham, Massachusetts, makes solar-powered compacting bins that hold about five times as much as a standard can and send a wireless alert when full.²⁸⁹ The company was approaching 100,000 units sold in 2023, and Philadelphia used them to cut Center City collections from more than 30 a week to about six.²⁸⁹ Boston maintains its bins in-house but, according to the company's CEO in 2023, was not using the bins' fullness data.²⁸⁹

Is garbage collection dangerous?

Yes. In the US, refuse and recyclable material collection is consistently among the deadliest civilian occupations. In 2024, 36 collectors died on the job, a rate of 37.4 deaths per 100,000 full-time workers, the fifth-highest of any occupation, according to the Solid Waste Association of North America (SWANA), citing Bureau of Labor Statistics data.²⁹⁰ In 2023 there were 41 deaths and a rate of 41.4, fourth-highest; in 2022 the rate was 22.6.²⁹⁰

Crews work in traffic, often before dawn, around heavy hydraulic equipment. New York's commercial waste zone law includes new safety standards for private carters.²⁷¹

For comparison, the Bureau of Labor Statistics counted 5,070 fatal work injuries across all US occupations in 2024, a rate of 3.3 per 100,000 full-time equivalent workers.²⁹¹ By those figures, collectors died at more than ten times the all-worker rate.

How do cities fight rats?

Rats follow food, and a bag on the sidewalk is food. The current strategy in several cities is to take away the buffet with containerization: requiring trash to go into sealed bins instead of bags on the curb.

New York phased this in. Businesses have had to containerize for about two years as of late 2025; buildings with one to nine units were added in November 2024; and more than 70% of the city's trash must now be in containers.²⁹² Manhattan Community Board 9 (West Harlem) became the first fully containerized district in June 2025, with Brooklyn Community Board 2 next in 2026.²⁹² DSNY reported that 311 rat sightings fell from 25,230 (December 2023 to November 2024) to 20,025 (December 2024 to November 2025), a 20.6% drop, with 12 straight months of year-over-year declines.²⁹²

Those are counts of 311 reports, a proxy for complaints rather than a census of rats (more on the system in 311, the wires under the street, and city data).

In Boston, the city released a multi-department Rodent Action Plan in July 2024 that puts prevention ahead of extermination. "We can't poison our way out of a problem like this," said Chief of Operations Dion Irish.⁹⁵ The plan piloted rodent-resistant cans on Boston Common, in parks and on North End streets, and named hot spots including Downtown, Chinatown, the North End, Allston/Brighton, Back Bay, South Dorchester and Roxbury.⁹⁵ The city's 2024 RFI also asked about containerization and route optimization partly as rodent control.⁶⁰

What's changing now (2026)

• Commercial waste zones keep rolling out in New York. After Queens Central, other zones are being phased in.²⁷¹
• Containerization spreads. Brooklyn Community Board 2 is next in line for full containerization in 2026.²⁹²
• Boston's contracts come up. Most of Boston's collection and disposal contracts run to around June 2027, so the city's next round of choices about trucks, bins and disposal is being set now.⁶⁰
• Boston composting grows. The curbside food waste program is adding households from its waitlist in fall 2026.²⁸⁵
• EPR moves from law to invoices. Seven states have laws, Oregon is collecting producer fees, and five more states were assessing as of late 2025.²⁸¹²⁸³
• The data gap persists. EPA's national numbers still stop at 2018.²⁶³

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13Keeping streets clean and open

The short version: A street sweeper or a snowplow can only clear what it can reach, so most of street cleaning is really the work of getting parked cars out of the way: posted sweeping days, snow emergency parking bans, tow trucks and alerts. In Boston, residential streets are swept by day from April through November and main roads are swept at night all year. When the city declares a snow emergency, cars must come off main roads or be towed. The famous Boston space saver is tolerated only during a declared snow emergency and for 48 hours after it ends, and never in the South End or Bay Village.

How it changed: from rivers of manure to uniformed sweepers

In the 1890s, New York's streets were covered in an estimated 2.5 million pounds (about 1,100 tonnes) of horse manure a day, plus 60,000 gallons (227,000 liters) of urine; dead horses were left in place and garbage lay a foot or two deep.²⁶⁵ (The widely repeated tale of an 1894 "Great Horse Manure Crisis" is a different matter: its famous quote has never been found and traces to a 2004 article, as Where your trash actually goes explains.²⁶⁶)

When sanitary engineer George E. Waring Jr. took over New York street cleaning in 1895, his first step was about the curb, not the broom: a law requiring horses and carts to be stabled overnight instead of left standing in the street.²⁶⁵ That is the same logic as a modern sweeping-day tow zone: the street has to be empty before it can be cleaned.

Waring's sweepers wore white uniforms and pith helmets and pushed wheeled carts, and the city held a parade honoring the department in 1896.²⁶⁵ Snow was handled the simple way: it was dumped in the rivers.²⁶⁵

The white uniforms earned the sweepers the nickname "White Wings."²⁶⁷

Why do cities tow cars for street sweeping?

A mechanical sweeper runs along the gutter, where litter, leaves, grit and sediment collect against the curb. A parked car blocks that strip completely, and the sweeper has to swing around it, leaving the dirt behind. That makes sweeping programs mostly parking programs: signs that name a day and time window, tickets for cars left in place, and tows for the worst cases.

Sweeping also matters below the street. What the sweeper does not pick up can wash into storm drains in the next rain, so a clean gutter is partly a stormwater measure. (More on stormwater in Where it goes after you flush (or it rains).)

In Boston: street sweeping rules

Boston runs two programs, according to the city's Public Works Department:²⁹³

Residents can sign up for No-Tow alerts through the city's Notify Boston system.²⁹³

If your car is towed, the city lists the costs as a $132 tow fee plus $35 a day in storage and a fuel surcharge, before any parking ticket.²⁹³

As of September 2026, Boston's parking clerk lists a $40 fine for a street cleaning violation and $90 for overnight street cleaning (no tow), with late penalties of $13 and $30.²⁹⁴

What is a snow emergency?

A snow emergency is a formal declaration by a city that changes the parking rules so plows can clear the main roads curb to curb. The details vary by city; what follows is Boston.

When Boston declares a snow emergency, cars parked on main roads are ticketed and towed.⁸² To give people somewhere to put their cars, the city arranges discounted garage parking from two hours before the declaration until two hours after it is lifted.⁸²

How does Boston plow and salt?

The Public Works Department runs plowing and salting. Under Mayor Marty Walsh, the city launched Boston Snow Stats, a public page showing the number of plows on duty, miles plowed, salt used and the percent of streets plowed, searchable by address.²⁹⁵

The scale is large: in one season, a Public Works update (undated on the city's site) reported more than 74,862 tons of salt applied and nearly 19,000 truckloads of snow removed.⁸³ Going into the 2024-25 winter, the city said it had 175 pieces of equipment ready to clear roads, could put 800 on the streets with contractors during a snow emergency, and had 34,000 tons of salt on hand.²⁹⁶ Removal is a separate job from plowing: plows push snow to the side, and in a big storm the banks themselves have to be scooped up and trucked away to keep lanes, crosswalks and hydrants open.

Many cities also spray roads with brine, a salt-water solution, before a storm so snow does not bond to the pavement.

Are space savers legal in Boston?

A space saver is an object, often a lawn chair, a traffic cone or a trash barrel, that a Boston resident puts in a parking spot they shoveled out, to claim it while the car is away. It is a neighborhood custom, not a property right. The city's rules, as of October 2026, are narrow:⁸²

• Only during a declared snow emergency. Space savers are allowed only while a snow emergency is in effect. A regular snowfall without a declaration does not count.
• 48 hours after it ends, they must go. Once the snow emergency is lifted, space savers must be removed within 48 hours.
• Never in the South End or Bay Village. Space savers are banned in both neighborhoods.

The rules have firmed up over time. An earlier city notice from the Walsh administration in 2015 described the 48-hour limit as "a guideline," and the South End ban at that time was a winter pilot.²⁹⁷ The same notice said Public Works crews remove space savers on trash day.²⁹⁷ The current city page states the 48-hour removal as a requirement and lists the South End and Bay Village bans.⁸²

In our reading, the gap between custom and rule is where neighbors clash. A chair still out a week after the emergency ends is outside what the city tolerates, whatever the block's custom says. The space saver is a short window the city allows, not a claim on public curb space.

Who clears the sidewalk?

Sidewalks and bins sit in the same strip of street as the gutter. Trash bags on the curb are both litter and rat food, which is why several cities are moving trash off the sidewalk and into sealed containers. In New York, more than 70% of trash had to be containerized as of late 2025, and Manhattan Community Board 9 in West Harlem became the first fully containerized district in June 2025.²⁹² In Boston, the July 2024 Rodent Action Plan piloted rodent-resistant cans on Boston Common, in parks and on North End streets.⁹⁵

Public litter bins matter too. Solar compacting bins from Bigbelly, a Needham, Massachusetts company, hold about five times a standard can and send a signal when full; Philadelphia used them to cut Center City collections from more than 30 a week to about six.²⁸⁹ Boston maintains its bins in-house, but the company's CEO said in 2023 that the city was not using the bins' fullness data.²⁸⁹

Boston requires property owners to clear sidewalks and curb ramps within three hours after snow stops falling, or within three hours after sunrise if it snowed overnight, leaving a path at least 42 inches wide.²⁹⁸ Fines for an uncleared sidewalk are $200 a day for commercial properties, $100 for residential buildings with more than 16 units and $50 for smaller ones; shoveling snow into the street is also prohibited and fined.²⁹⁸

What's changing now (2026)

• Bags off the curb. New York's containerization rollout continues, with Brooklyn Community Board 2 next to go fully containerized in 2026.²⁹² For street cleaning, the likely effect is fewer torn bags and less loose litter in the gutter.
• Data in public. Boston publishes live plowing statistics through Snow Stats and sends No-Tow alerts for sweeping through Notify Boston.²⁹⁵²⁹³
• Space saver rules are now stated as rules. The city's current snow page presents the 48-hour removal and the South End and Bay Village bans as requirements, not guidelines.⁸²

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14From fire alarm boxes to 911

The short version: Boston switched on the world's first municipal electric fire alarm telegraph in 1852, and in 2026 it still keeps about 1,250 red street boxes wired to a central office. Telephone emergency numbers came much later: 999 in London in 1937, 911 in the US in 1968, and 112 across the European Union, adopted in 1991. A modern US call is routed by the caller's location to a call center and logged in dispatch software, and fire crews are often measured against a national response-time standard. The system is now moving from analog phone trunks to internet-protocol networks that can carry text, photos and floor-level location.

What was the first fire alarm system?

Before the telegraph, a fire was reported by running to a fire house, shouting, or ringing a church bell, and the alarm spread as fast as people could run. Boston changed that on April 28, 1852, when its electric fire alarm telegraph went into service, the first municipal system of its kind in the world.⁷⁸ The first alarm came in the next day, April 29, at 8:25 p.m.⁷⁸

The system was invented by Dr. William F. Channing, and Moses G. Farmer helped develop and build it. Farmer became the first superintendent of fire alarm telegraph.⁷⁸ The 1852 network was small by later standards:

• 40 street boxes
• 16 alarm bells
• 3 box circuits and 3 bell circuits⁷⁸

The idea is a fire alarm telegraph: a network of street boxes wired to a central office, where each box identifies itself by its box number when someone pulls the handle. The office then knows which street corner the alarm came from without anyone speaking a word.

The Adams County Museum describes the mechanism in a Gamewell call box: pulling the hook or turning the knob releases a spring-loaded wheel that taps out a pulsed electrical signal matching the box's number, and at the receiving end the number is matched to a list of box locations.²⁹⁹

The IEEE, the electrical engineers' professional body, named Boston's system an engineering Milestone on October 1, 2004, with a plaque at the Boston Fire Department office at 59 the Fenway.⁷⁸ According to the IEEE's history site, the alarm office moved into a fire-resistant building in 1925, gained electronic decoding terminals in 1988, and the network runs independently of telephone and electric utility lines.⁷⁸

Who was Gamewell?

Boston invented the system; a South Carolinian turned it into an industry. Channing and Farmer's patent, "Electromagnetic Fire Alarm Telegraph for Cities," was acquired by John Gamewell.³⁰⁰ After the Civil War, Gamewell partnered with Kennard and Company, and they opened a factory in Newton Highlands, Massachusetts, in 1873.³⁰⁰ By 1886 the Gamewell system ran in more than 250 cities in the US and Canada.³⁰⁰ The company moved to a factory in Newton Upper Falls in 1889 and stayed there until the 1970s, when it became a division of Gulf and Western.³⁰⁰

That is why cast-iron alarm boxes in very different cities often look like cousins: many came from the same few factories outside Boston.

The 1872 fire and the locked boxes

Twenty years after the telegraph opened, it faced its worst test. The Great Boston Fire began on the evening of November 9, 1872. Wikipedia's account puts the start at 7:20 p.m. and the first alarm, from Box 52 at Summer and Lincoln streets, at 7:24 p.m.³⁰¹

The delay that mattered came before anyone could pull the hook. "All of the fire alarm boxes were kept locked," and only a few citizens in each area held keys.³⁰¹ Firefighters arrived about twenty minutes after the fire was first noticed.³⁰¹ The department's horses had also been weakened by an outbreak of equine influenza, but the post-fire commission found the delay from the missing horses was only "a few minutes."³⁰¹ Calls for help to other towns were slowed because most telegraph offices had closed for the night.³⁰¹

The toll was 776 buildings on about 65 acres (26 hectares) and $73.5 million in damage, about $1.98 billion in 2025 dollars.³⁰¹ Deaths are reported as anywhere from 26 to "at least 30," including 11 firefighters.³⁰¹ Sources disagree on the details: different parts of the same Wikipedia article give different start times and death tolls, and both the locked boxes and the horses should be read as reported factors, not settled single causes.

Are fire alarm boxes still used?

In Boston, yes. As of April 2026, the city has about 1,250 street fire alarm boxes and about 1,200 master boxes, which connect schools, hospitals, libraries and other buildings straight to the fire department.⁷³ A team of 13 maintains the network, and vehicle crashes are a common cause of damage.⁷³ Box numbers now appear on a computer screen at the alarm office instead of on punched ticker tape.⁷³

The count has fallen. In 2013 Boston had "nearly 2,200" street-corner boxes and issued a request for information on how to modernize them; false alarms made up roughly 90 percent of box alarms at the time.³⁰² The 2013 and 2026 figures may not count the same things, so treat the drop as a trend, not an exact number. The IEEE's history site gives yet another older count of about 1,500 street boxes and over 1,000 master boxes.⁷⁸

The case for keeping them was made in June 2024, when a 911 outage hit and Police Commissioner Michael Cox told residents to use the street boxes.⁷³ Our reading: a separate wired network that does not depend on the phone system is the point of the boxes, not a leftover. (More on what runs under the pavement in 311, the wires under the street, and city data.)

Not every city agrees the cost is worth it. Salem, Massachusetts, is decommissioning its system because of cost.⁷³ New York City tried to remove about 15,000 street emergency boxes, but in 2011 a court denied the request.³⁰³ The court found that the city's proposed alternative, street pay phones with a tapping protocol, would discriminate against deaf people under the Americans with Disabilities Act, and it left in place a 1996 injunction won for the Civic Association of the Deaf.³⁰³

How it changed: 999, 911 and 112

The street box tells responders where. The telephone added what, but needed an operator, and in an emergency the operator could be the bottleneck.

London, 1937. The world's first emergency telephone number, 999, launched in London on June 30, 1937.³⁰⁴ It was prompted by a 1935 fire in Marylebone that killed five women.³⁰⁴ On July 7, 1937, a 999 call led to an arrest about four minutes later.³⁰⁴ The number reached Glasgow in 1938 and the whole of the UK in 1976.³⁰⁴

The US, 1968. Fire chiefs urged a single national number in 1957, and in 1967 the President's Commission on Law Enforcement and Administration of Justice recommended one.³⁰⁵ The first 911 call was made on February 16, 1968, in Haleyville, Alabama, on the Alabama Telephone Company network: Alabama House Speaker Rankin Fite called Rep. Tom Bevill at the police station.³⁰⁵ Adoption was slow. 911 covered 17 percent of the US population in 1976 and 50 percent by 1987.³⁰⁵

The EU, 1991. Council Decision 91/396/EEC, of July 29, 1991, introduced 112 as the single European emergency number, to run alongside national numbers, with a 1996 deadline for public networks.³⁰⁶ Later EU laws added free calls, caller location (2002), access from internet phone services (2009) and eCall, the automatic crash call from cars (2012-2013).³⁰⁶

Other countries use their own numbers. In Australia, Triple Zero (000) is the main emergency number, 112 also works from mobile phones, and 106 serves TTY users.³⁰⁷ In Japan and South Korea, 119 reaches fire and ambulance services, while police use 110 in Japan and 112 in South Korea.³⁰⁸

The scale today in the US: about 240 million 911 calls a year, with 80 percent or more from wireless devices in many areas, answered at 5,748 primary and secondary call centers (that center count dates from February 2021, and the call estimate is undated).³⁰⁹

How does 911 know where you are?

The call center that answers 911 is a PSAP, a public safety answering point. In legacy "Enhanced 911," the call travels through the phone company's network to a selective router, a switch that picks the right PSAP, and the PSAP then looks up the caller in the ANI/ALI databases: automatic number identification and automatic location identification.⁹⁹

That worked well for landlines tied to a street address. Mobile phones broke the model, so US rules came in stages. Phase I delivers the cell tower and sector; Phase II adds the caller's estimated coordinates. As of February 2021 data, at least some Phase II location was available at 99.2 percent of PSAPs, covering 98.9 percent of the population.³⁰⁹

The next problem is height. A dot on a map does not tell responders which of 40 floors to search. In March 2025 the FCC proposed reporting vertical location, the z-axis, as height above ground level and adding floor-level estimates.³¹⁰ Nationwide carriers would get 24 months to deploy either dispatchable location (a street address plus details like floor or apartment) or validated z-axis technology.³¹⁰ The FCC also asked how to improve location for text-to-911, which "currently lacks precise location data," and whether to retire the legacy Phase II rules.³¹⁰

The FCC's existing rules required wireless carriers to meet horizontal accuracy requirements for 80 percent of calls by April 2021.³¹¹ For height, a 2019 FCC order (published January 16, 2020) adopted a z-axis metric of 3 meters above or below the handset for 80 percent of indoor wireless 911 calls from z-axis-capable devices, which nationwide carriers had to meet in the top 25 markets by April 3, 2021, and the top 50 by April 3, 2023.³¹¹ A July 2020 FCC order required nationwide carriers to provide z-axis capability by 2025 and gave non-nationwide carriers an extra year, until April 2026.³¹²

A US call today goes roughly like this: the caller dials, the carrier attaches a number and a location estimate, and a router picks the PSAP. A call-taker answers, sees the location on a map, and enters the incident into dispatch software; a dispatcher then sends units.

Dispatch, response times and radio

CAD, computer-aided dispatch, is the software that logs each incident and helps assign units; AVL, automatic vehicle location, tracks response vehicles by GPS so dispatch can see which one is closest. That is the general shape; vendors and cities set them up differently.

Phoenix's regional dispatch center gives one example: its CAD uses GPS to know where every unit is, recommends units based on preset response requirements for each call type and the known location of available units, and an operator reviews and can change the recommendation before dispatching.³¹³

How fast are fire crews supposed to arrive? Many US fire departments measure themselves against NFPA 1710, a consensus standard for career fire departments. As summarized by the District of Columbia's fire department, it sets:

Departments are expected to meet these on at least 90 percent of incidents.³¹⁴

How do responders talk? Radio is the other half of dispatch. P25 (Project 25) is a digital radio standard meant to let public safety radios from different makers work together, and P25 equipment goes through a federally backed Compliance Assessment Program that decides whether it can be bought with grant money.³¹⁵ Alongside radio, US agencies increasingly use FirstNet, a public safety broadband network. The FirstNet Authority was created by a 2012 law; in March 2017 it signed a 25-year contract with AT&T, which runs the network on 700 MHz Band 14.³¹⁶ AT&T finished the initial buildout in March 2023, and by the end of 2024 the network had over 6.7 million connections and 29,500 agencies.³¹⁶

How does the alert reach my phone?

In the US, the loud buzz on your phone for a flash flood or a missing child is a Wireless Emergency Alert (WEA). The first one went out on June 28, 2012: a National Weather Service flash flood warning near Santa Fe, New Mexico.³¹⁷ The path runs from an authorized warning in a standard format (CAP) to FEMA's IPAWS hub, then to wireless carriers, then out as a cell broadcast that phones in the area receive, with no app needed.³¹⁷ The message limit rose from 90 to 360 characters in 2020, and the Weather Service alone had sent about 60,000 WEAs as of 2022.³¹⁷

Because it is a broadcast from the tower, not a text to each number, the system does not need to know who is in the area, which is also why everyone in a crowded room tends to get the alert at once.

What is 988?

Since July 2022, the US has had 988, a three-digit number for the Suicide and Crisis Lifeline, as an alternative to 911 for people in mental health crisis.³¹⁸ From July 2022 through September 2025, about 19.1 million calls, texts and chats were routed to crisis centers. Over that time calls rose about 87 percent, texts about 260 percent and chats about 23 percent.³¹⁸ As of March 2026, 988 calls are georouted by the caller's approximate location, and texts are to follow by April 2027, according to a July 2026 GAO review.³¹⁸

In Boston

Boston runs both eras side by side. The 1852 telegraph's descendants, about 1,250 street boxes and 1,200 master boxes, are maintained by a 13-person team, and they served as a backup during the June 2024 911 outage.⁷³ Boston's boxes are also the basis of Alarm Club, a street game built on the 1852 network.

On the medical side, Boston EMS's 2024 figures give a sense of a big-city ambulance service's workload:⁹⁶

• 140,701 clinical incidents and 166,422 responses
• 93,774 patient transports
• Peak staffing of 21 basic life support and 5 advanced life support ambulances from 17 stations
• 472 budgeted full-time positions

Its median response time for Priority 1 calls, the most urgent, was 7.3 minutes in 2024, against the service's own goal of 6.0 minutes.⁹⁶

What's changing now (2026)

Next Generation 911. The biggest change is under the hood. NG911 replaces analog phone trunks and selective routers with an IP network, the ESInet (Emergency Services IP Network), which can carry text, images and rich location data to the PSAP.⁹⁹ The FCC adopted its NG911 order in July 2024; it took effect November 25, 2024, and its information-collection provisions became enforceable March 25, 2025.⁹⁹³¹⁹ It works in two phases:

• Phase 1: phone and internet providers must deliver 911 traffic in IP (SIP) format to the ESInet.⁹⁹
• Phase 2: they must use standard NG911 signaling, embed the caller's location in the call itself, and use a location server.⁹⁹

The clock starts only when a 911 authority files a valid request. Nationwide wireless, internet phone, text and most landline providers then get 6 months per phase; rural incumbent landline carriers, smaller wireless carriers and internet relay providers get 12 months.⁹⁹ Because each state or region has to build its ESInet and file requests, NG911 coverage in 2026 likely varies a great deal by place.

Massachusetts was early: according to the State 911 Department, its new digital statewide system went live in December 2017, replacing the analog one, with 232 PSAPs at the end of 2018 and text-to-911 added around the turn of 2019.³²⁰

Floor-level location. The March 2025 FCC proposal on z-axis and floor-level location is the other live rulemaking, aimed at the tall-building problem.³¹⁰

FirstNet's future. FirstNet's authorization is due for renewal by February 2027.³¹⁶

988 routing. Location-based routing for 988 calls started by March 2026, with texts scheduled by April 2027.³¹⁸

The boxes. Boston is keeping its street boxes while neighbors such as Salem take theirs down.⁷³ The choice comes down to how much to spend on a parallel alarm system that is mostly idle until the day everything else fails.

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15311, the wires under the street, and city data

The short version: 311 is the non-emergency front door to city government in the US and Canada: a phone number that grew into apps and websites for reporting potholes, graffiti and missed trash pickups. Behind it sits a layer of private telecom in and on the street, from small cell antennas on streetlights to buildings where internet networks meet. Cities increasingly publish the data these systems produce, and some have tried to wire whole districts with sensors. Who controls that data, and what the city is allowed to do with it, has turned out to be the hard part.

What is 311 and when did it start?

311 is a three-digit number, and now usually an app and website as well, for non-emergency city services and information. It started as a way to take pressure off 911. Baltimore, Maryland, launched the first 311 service on October 2, 1996, for police non-emergency and information calls.⁹¹

A few months later the federal government made it national. The FCC's First Report and Order FCC 97-51, adopted February 18, 1997, and in effect from March 28, 1997, assigned 311 across the US for non-emergency police and other government services. The same order assigned 711 for relay services.³²¹

Other countries chose their own numbers:

• Canada: the regulator, the CRTC, reserved 311 on November 5, 2004, and Calgary launched first, on May 18, 2005.⁹¹
• Germany: 115 is the government services number.⁹¹
• UK: 101 is the number for non-emergency police.⁹¹

How it changed: from hotline to service desk

The model that most big cities copied came from New York. NYC311 launched in March 2003.⁹¹ Its biggest single day came on December 20, 2005, the first day of a transit strike, when it took a record 240,000 calls.⁹¹ By then 311 was less a police overflow line than the place people called when the city itself had stopped working.

By fiscal year 2026, NYC311 handled far more than phone calls:³²²

Falling call counts alongside large app and web numbers suggest a shift from phone to digital channels, though one city's figures cannot prove a national pattern.

Open311. Each city's 311 system started as its own software, which made it hard for outside apps to file requests. On March 3, 2010, US Federal CIO Vivek Kundra announced Open311, a uniform API, an open standard for submitting and tracking service requests.⁹¹ The UK's FixMyStreet, a citizen reporting site, uses it.⁹¹ In plain terms, Open311 lets a request typed into a third-party app land in the same queue as one phoned in to the city.

In Boston: Citizens Connect and the 311 app

Boston was early to the smartphone version. A July 2009 report described Citizens Connect, an iPhone app conceived by mayoral aide Nigel Jacob and built by Connected Bits, a New Hampshire company, for a $25,000 support fee.⁸⁹ The flow it set up is still the basic pattern for city reporting apps: a resident photographs a problem such as graffiti or a pothole, the phone's GPS records the location, and the resident gets a tracking number to follow the request.⁸⁹

The app launched in October 2009 as Citizens Connect and is now called BOS:311.³²³ The renaming came on August 11, 2015, when Mayor Martin J. Walsh launched BOS:311 and existing Citizens Connect users were upgraded automatically.³²⁴ Reports from the app made up 6% of all service requests tracked in the city's systems in 2010 and roughly 28% by 2014.³²³ The city publishes the reports filed through the app as a downloadable dataset on its open data portal.³²³ WBUR counted 287,148 Boston 311 requests in 2024 through December 10; parking was the most common category, at 60,423, followed by street cleaning, at 21,873.³²⁵

Why are there antennas on streetlights?

Look up at a city streetlight or wooden utility pole and you may see a gray box or cylinder that is not a light. That is often a small cell, a low-power cell site that adds mobile capacity over a short range. 5G signals travel short distances, so carriers need many small sites, often on streetlights, utility poles or buildings.⁵⁴ (More on the poles themselves in How streetlights work.)

Each of those sites sits on public property or in the public right of way, which gives cities a say. In the US, the FCC limited that say in its small cell order, adopted September 26, 2018, and in effect from January 14, 2019:⁵⁴

• Shot clocks: cities get 60 days to decide on attaching a small cell to an existing structure and 90 days for a new structure.
• Fees: presumptively lawful fees are up to $500 one-time and $270 per year per site.

Municipalities challenged the order in court, in the Ninth Circuit.⁵⁴ Broadly, the dispute was over local control versus speed of deployment: carriers and the FCC argued for faster, cheaper permitting, and cities argued for keeping authority over their streets and fees.

On August 12, 2020, the Ninth Circuit upheld most of the order, including the fee limits and shot clocks, in City of Portland v. United States.³²⁶ It struck down two of the order's tests for local aesthetic rules: that they be "objective" and "no more burdensome" than rules for other infrastructure.³²⁶ The US Supreme Court declined to hear the case on June 28, 2021.³²⁶

The wires under the street

The visible antennas are the end of a much larger network. Under most city streets run conduits carrying fiber and copper for phone companies, cable companies and the city's own systems, and in older cities such as Boston the fire alarm boxes still run on their own wired loops, separate from the phone and power networks.⁷⁸ (Their history is in From fire alarm boxes to 911.)

The companies that use those conduits need the city's permission. In Boston, the city is the licensing authority for cable television, and its Broadband and Cable Office works with Verizon (Fios), Comcast (Xfinity) and Astound (RCN) on their license agreements.³²⁷ Comcast of Boston has held one of the city's cable franchises since July 17, 2002, and when a license comes up for renewal the city takes public comment and reviews the operator's service quality and complaint handling.³²⁷

Whether cities should run their own internet service is contested in the US. A BroadbandNow report, last updated in July 2025, counted 16 states with laws that substantially hinder municipal broadband networks.³²⁸ Supporters cite networks such as Chattanooga's municipal fiber as a way to add competition and close the digital divide; incumbent telecom companies have lobbied and campaigned against such projects in several states.³²⁸

Where does Boston's internet meet?

Data does not travel from your phone to a website on one company's wires. Networks hand traffic to each other, and they do it in specific buildings. A carrier hotel is a building where many telecom networks place equipment and interconnect. Inside, an internet exchange point (IXP) is a shared switch where networks swap traffic directly instead of paying a third party to carry it.

In Boston, that place is One Summer Street, a datacenter run by Markley Group. The Boston Internet Exchange runs there, with a second site in Lowell; it went online in 2012 and has 48 members.⁹⁰ In practice, traffic between two networks that both connect there can stay in Boston instead of making a round trip through New York or Virginia.

What is open data?

An open data portal is a government website that publishes datasets for anyone to download and reuse. Boston's, Analyze Boston, went live on April 6, 2017, after a beta in February.³²⁹ The city's Analytics Team and its Department of Innovation and Technology built it on CKAN with OpenGov.³²⁹ At launch it held about 115 datasets, including CityScore, food inspections and public safety data, all with API access and public domain licensing.³²⁹

Smart cities: sensors, platforms and digital twins

"Smart city" covers several very different ideas. Three examples show the range.

An open sensor platform: Barcelona. Sentilo is an open-source platform for sensors and actuators, sponsored by Barcelona City Council's Municipal Institute of Informatics.³³⁰ It grew out of a smart city strategy begun in November 2011, with a platform start date of January 2014, and it is dual-licensed under the EUPL and LGPL so other cities can reuse it.³³⁰ Barcelona tested noise, air, traffic and waste sensors.³³⁰

A digital twin: Singapore. A digital twin is a detailed digital model of a city or system used to simulate and plan changes. Virtual Singapore launched on December 3, 2014, as part of the country's Smart Nation program, and was completed in 2022.³³¹ It was co-led by the National Research Foundation, the Singapore Land Authority and GovTech, and built on Dassault Systèmes' 3DEXPERIENCE City software.³³¹ Its uses include planning, flood management, and simulations of wind, noise and traffic.³³¹

A private master plan: Toronto. Sidewalk Labs pulled out of Toronto's 12-acre (5 hectare) Quayside waterfront project in May 2020.³³² CEO Dan Doctoroff cited "unprecedented economic uncertainty" from the pandemic, and the project had drawn criticism, with disputes that included who would own its intellectual property and data.³³²

Our reading of the three: sensors and software are cheap compared with the governance around them. Barcelona made its platform open-source and city-sponsored; Singapore built its model under government agencies; Toronto's project ended with unresolved questions about who would own and control the data, alongside the economic reasons the company gave.

Is Boston using facial recognition?

Cameras and sensors raise a question that open data portals do not: what the city may collect about people, not about potholes. Cities have answered it differently, and the debate is ongoing.

On June 24, 2020, the Boston City Council voted unanimously to ban city use of facial surveillance, including obtaining it through third parties.³³³ The measure was sponsored by Councilors Ricardo Arroyo and Michelle Wu.³³³ It does not cover private companies or federal agencies.³³³ Police Commissioner William Gross said at the time that the department did not use the technology: "Until this technology is 100%, I'm not interested in it."³³³ WBUR reported that the vote made Boston the second-largest community in the world to ban the technology, after San Francisco.³³³

This guide takes no side in the wider debate; the record above is what Boston decided.

What's changing now (2026)

• Phone to app. NYC311's calls fell from 18.231 million in FY2022 to 16.609 million in FY2026, while app, text and web contacts ran into the millions.³²²
• Small cells under federal limits. The FCC's 2018 shot clocks and fee limits still shape how fast antennas go up on US streetlights.⁵⁴
• Digital twins as finished tools. Virtual Singapore moved from launch in 2014 to completion in 2022, and is now used for flood and planning work.³³¹
• Open data keeps growing. Analyze Boston started with about 115 datasets in 2017.³²⁹

As of October 2026, Analyze Boston lists 235 datasets.³³⁴

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16Who actually runs a city

The short version: No single body runs a modern city's systems. The mayor's office may own the streets, but the water in the pipes, the trains under them, the power in the wires and the airport at the edge of town often belong to separate commissions, state authorities and private companies, each with its own board, budget and rules. Boston is a clear case: a city-chartered commission runs the local water pipes, a state authority supplies the water and treats the sewage for 61 communities, and other bodies run the rest. Knowing who owns what is the first step to getting anything fixed.

Why doesn't the city run everything?

When people say "the city" fixed a water main or raised the fare, they usually mean several different organizations. A typical large city in the US or Europe is a patchwork of four kinds of body:

• City departments, which answer directly to the mayor or city manager and are paid for out of the city's own budget.
• Independent authorities and commissions: public bodies created by law to run one system, such as water, transit or an airport, with their own board and budget, outside day-to-day city control.
• State or regional agencies, which run systems that cross city lines.
• Private utilities, usually regulated companies, which own and run networks like electricity and gas.

The split usually follows the shape of the network. A street belongs to one city. A reservoir, a sewage plant or a rail line serves dozens of cities at once, so the body that runs it tends to sit above any one of them. Money matters too: a body that can charge its own fees and borrow on its own account can plan pipes and tracks over decades without waiting on the city's annual budget fight.

The cost of this arrangement is coordination. A single block of street can have a city road surface, a commission's water main, a state authority's sewer connection and a private company's gas line, all under one patch of asphalt, each owned by a different organization with a different schedule.

How does London do it?

London is a useful contrast because it pulls much of its transport into one body. Transport for London (TfL) was created in 2000 under the Greater London Authority Act 1999.³³⁵ It is an executive body of the Greater London Authority, and its board is appointed and chaired by the elected Mayor of London.³³⁵ TfL runs:

• the Underground, the Overground and the DLR
• the bus network, mostly operated by private companies under contract
• the trams
• the "red route" network of strategic roads
• the congestion charge and taxi licensing³³⁵

So in London, one mayor-led body runs trains, buses, main roads and the congestion charge together, while the borough councils handle more local services. Even there, "public" does not mean "run by public employees" end to end: the buses that TfL plans are mostly driven by private operators on contract.³³⁵

TfL's money shows how tangled the funding lines get. In its 2019-20 budget of £10.3 billion, fares supplied 47%, grants (mainly from the Greater London Authority) 33%, congestion charging and other income 12%, and borrowing 8%.³³⁵ Direct operating funding from the national government ended in 2018, though the national government provided emergency support during COVID-19.³³⁵

Many other big cities split power in their own ways.

In the Paris region, transit is planned and paid for by Île-de-France Mobilités, a regional body that coordinates RATP, SNCF and nearly 90 private bus companies.³³⁶ Its 33-member board is led by the Île-de-France Region and chaired by Valérie Pécresse, the region's president since 2015, rather than by the Mayor of Paris.³³⁷ Paris's drinking water, by contrast, is a city service: Eau de Paris, a municipal utility created on January 1, 2010, runs the whole system, from production to billing.³³⁸ Tokyo's 23 special wards each have their own elected mayor and assembly, but the Tokyo Metropolitan Government runs water supply, sewage disposal and fire services across the ward area, while each ward handles waste disposal.³³⁹ The metropolitan government also runs one of the city's two subway systems, the Toei Subway, through its Bureau of Transportation.³⁴⁰ Of Tokyo's roughly 24,431 km of roads, the metropolitan government's Bureau of Construction administers about 2,347 km.³⁴¹

In Boston

Boston shows the patchwork clearly, because water alone involves two separate public bodies, neither of them a city department.

The Boston Water and Sewer Commission (BWSC) was created by an act of the Massachusetts legislature in 1977.⁴⁴ It is "a corporate separate and apart from the City of Boston" and sets its own water and sewer rates.⁴⁴ It runs about 1,015 miles (1,630 km) of water main and 1,435 miles (2,310 km) of sewer and storm drain pipe.⁴⁴

BWSC does not make its own water. It buys it wholesale from the Massachusetts Water Resources Authority (MWRA), which delivers it into BWSC's system at 27 metered points.⁴⁴ The MWRA is a state authority that supplies wholesale water and sewage treatment to about 3.1 million people in 61 municipalities, plus more than 5,500 large industrial users.⁴⁵ Its water comes from the Quabbin Reservoir by way of the Wachusett Reservoir, and it treats sewage at Deer Island, at the mouth of Boston Harbor.⁴⁵ (The full trip is in Where your tap water comes from.)

So a glass of water in a Boston kitchen has passed through a state authority's reservoirs and aqueducts, crossed a meter into a city-chartered commission's mains, and will leave through that commission's sewers on its way to the state authority's treatment plant. The city government proper owns neither step.

Who runs what, as far as our sources confirm (as of October 2026):

On the streets themselves, the city's Public Improvement Commission owns and manages Boston's public and private rights-of-way.³⁵² Some of the busiest roads are state-run: as of 2021, DCR maintained Storrow Drive, Soldiers Field Road, Morrissey Boulevard and Day Boulevard, after a 2020 Baker administration proposal to transfer those four to MassDOT did not succeed.³⁵³

Who controls the money: mayor or council?

Boston is usually described as a strong-mayor city, and the budget fights of the past two years show what that looks like in practice. In the FY25 cycle, the council approved $15.3 million in budget changes, "only to have most of them vetoed by Wu."³⁴² In the FY26 cycle, the council's amendments came to $9.05 million, under 1% of the total, and passed unanimously on June 4, 2025.³⁴²

The FY27 budget was closer. In May 2026 the council "nearly rejected the proposal outright," and "the effort fell one vote short."³⁵⁴ The $1.7 billion schools budget passed 8-5.³⁵⁴ Mayor Michelle Wu accepted all but $1.4 million of the council's $11.8 million in amendments.³⁵⁴

Our reading: the council can push money around at the margins, a fraction of a percent of the total, and can threaten to block the whole budget, but the mayor sets the overall shape.

The rules come from the city charter. The mayor submits the budget by the second Wednesday in April.³⁵⁵ On November 2, 2021, 68% of Boston voters approved Ballot Question 1, which lets the council move money among existing or new line items as long as its total does not exceed the mayor's; the mayor can send the council's version back with further amendments, and the council can override those with a two-thirds vote.³⁵⁵

Cities elsewhere in the US often use a different model, in which an elected council hires a professional manager to run day-to-day operations. ICMA traces this form to Staunton, Virginia, which hired a "general manager" in 1908; Sumter, South Carolina, was the first city to formally adopt the plan, in 1912, and Dayton, Ohio, became the first sizable city to use it in 1914.³⁵⁶

According to the National League of Cities, council-manager is the most common form of city government in the US; in ICMA surveys its use grew from 48% of responding municipalities in 1996 to 55% in 2006.³⁵⁷ Mayor-council is the second most common and is found mostly in older, larger cities, such as New York and Houston, or in very small ones.³⁵⁷

How it changed

The patchwork in Boston was built in layers, mostly by the state legislature rather than by the city.

• 1977: the legislature creates BWSC as a body separate from the city, with power to set its own water and sewer rates.⁴⁴
• 1985: the MWRA is created, splitting off from the older Metropolitan District Commission.⁴⁵
• 2000: the MWRA finishes a deep-water sewage outfall from Deer Island as part of the Boston Harbor cleanup.⁴⁵

London went the other way at about the same time, gathering transport under one body: TfL was created in 2000 and placed under the new elected mayor.³³⁵

What's changing now (2026)

The pressure in 2026 is mostly about money, which shows up as tension between bodies. Boston's FY27 budget grew 2.1%, its lowest growth since FY10, and the city's release blames "the Commonwealth's rigid limitations on municipal revenue generation and diversification."³⁵⁸ In other words, the city says state law limits how it can raise money, which is another layer of the patchwork: the state runs agencies inside Boston and also sets the rules for how the city may tax. Who pays for the city covers that in detail.

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17Who pays for the city

The short version: A city runs on two budgets. The operating budget pays for this year's services - salaries, fuel, health insurance - and in US cities it leans heavily on the property tax. The capital budget pays for things that last decades, such as schools, roads and pipes, and is mostly borrowed through municipal bonds. On top of that sit fees for water and sewer, aid from the state, and US federal grants such as the 2021 infrastructure law, whose program authority reached its expiry date on September 30, 2026.

What's the difference between an operating and a capital budget?

The operating budget is the yearly spending plan for running services: the people who staff schools, plow streets and inspect buildings, plus their health insurance, fuel and supplies. It has to balance each year, and it is paid mostly from taxes, fees and aid.

The capital budget (or capital plan) is a multi-year plan for building or repairing long-lived assets: school buildings, bridges, fire stations, roads. Because those assets last decades, cities usually borrow to pay for them and repay the loans over time, so that the people who use a school over 30 years help pay for it.

Boston's numbers for the current year show the scale. On April 8, 2026, Mayor Michelle Wu filed a $4.9 billion operating budget for FY2027 and a $4.4 billion five-year capital plan for FY2027-2031.³⁵⁸ The council passed both in June 2026; the capital plan funds 321 projects.³⁵⁴ Boston Public Schools receive $1.7 billion of the operating budget.³⁵⁸ The capital plan includes $135 million for White Stadium.³⁵⁹ In the previous year's plan, nearly $1.2 billion of the capital budget (about 27%) was for school buildings.³⁶⁰

The two numbers look similar, but they are not comparable. The $4.9 billion is spent in one year. The $4.4 billion is spread over five.

Where does a US city's money come from?

For most US cities, the biggest single source is the property tax: a yearly tax on the assessed value of land and buildings. In 2015, the property tax made up 67% of Boston's operating revenue.³⁶¹ For FY27, the city's budget office puts the net property tax levy at $3.61 billion, 73.1% of the city's revenue.³⁶²

The FY27 budget documents give partial figures. The city expects $538 million in state aid, 10.9% of its budget, or $119.6 million after state assessments are subtracted.³⁶³ Local revenue, which includes excise taxes, is budgeted at $753.0 million, 15.4% of the revenue budget; the largest excise is the hotel room occupancy tax, at $162.1 million.³⁶⁴ The city calls the property tax its primary revenue source.³⁶³

The other main sources are:

• State aid. Money the state sends to cities, often for schools. In Massachusetts, the state also takes money back through "assessments," such as charter school tuition. Boston's net state aid - aid minus assessments - fell 46.2% over the ten years to FY15.³⁶¹ Again, the figure is dated.
• Federal funds. In the FY26 budget, federal funds supported more than $300 million a year in Boston city services.³⁶⁰
• Fees and charges. Permit fees, parking fines and, in many cities, water and sewer bills (the system those bills pay for is in Where your tap water comes from).
• Borrowing. Used for capital projects, not for day-to-day services.

London's transport body is a useful non-US contrast, because it runs largely on fares rather than property. In TfL's 2019-20 budget of £10.3 billion, fares supplied 47%, grants 33%, congestion charging and other income 12%, and borrowing 8%.³³⁵

What is Proposition 2½?

In Massachusetts, the property tax has a hard legal cap. Proposition 2½ was approved by voters in 1980 and took effect in FY1982.³⁶⁵ It sets two limits on the total property tax a city or town can raise, called the levy:

• The levy limit can rise 2.5% a year, plus "new growth" from new construction. Rising market values on existing property do not count as new growth.³⁶⁵
• The levy ceiling is 2.5% of the total assessed value of all property in the town.³⁶⁵

Voters can loosen the cap in two ways. An override permanently raises the levy limit and needs a majority vote.³⁶⁵ A debt exclusion or capital exclusion raises the levy temporarily to pay for a specific capital project.³⁶⁵

Boston collects the maximum property tax Proposition 2½ allows.³⁴² Its FY27 budget "does not seek an override for additional revenue beyond what is allowed by Proposition 2 ½."³⁵⁸ In practice, that means Boston's property tax revenue can grow by about 2.5% a year plus whatever new buildings add, however fast its costs rise. In FY27, health insurance costs alone were projected to rise $97.3 million.³⁵⁸

The cap also shapes who pays. Falling downtown office values are shifting Boston's tax burden toward homeowners.³⁴² The mechanism is arithmetic: when the total the city may collect is capped and one kind of property loses value, the other kinds pick up a larger share.

Why are water bills separate from taxes?

Many US cities run water and sewer as an enterprise fund: a self-supporting account inside city government, where customers' bills pay the system's costs rather than the property tax. Boston takes the idea further. Its water and sewer system belongs to the Boston Water and Sewer Commission, a body created by state law in 1977, separate from the city, which sets its own water and sewer rates.⁴⁴ BWSC in turn buys water wholesale from the MWRA.⁴⁴

Because the commission is separate from the city, the water bill pays for the pipes, and as far as our sources show, those dollars sit outside the city's $4.9 billion operating budget. (More on how these bodies fit together in Who actually runs a city.)

How do municipal bonds work?

A municipal bond is a loan that investors make to a state, city or public authority, which repays it with interest over a set period. Cities sell bonds to pay for capital projects. The market is large: US municipal bonds outstanding totaled $4.5 trillion as of the second quarter of 2026, up 4.8% from a year earlier, and issuance from January through September 2026 came to $473.8 billion.³⁶⁶

A city's bond rating works like a credit score: the higher the rating, the lower the interest it pays. As of its FY26 budget, Boston had held a AAA rating, the top grade, for 10 years.³⁶⁰

In the US, interest on state and local government bonds has been free of federal income tax since the income tax began in 1913, and that exemption lowers the cost of borrowing for states and cities.³⁶⁷

In Boston

Boston's budget in 2026 is a story of slow growth under pressure.

• FY26. Wu filed a $4.8 billion operating budget and a $4.5 billion capital plan on April 10, 2025, growth of 4.4% over FY25.³⁶⁰ It was signed on June 9, 2025.³⁴²
• FY27. The $4.9 billion budget grew 2.1%, the lowest since FY10.³⁵⁸ The city had a $48.4 million FY26 gap to close, and reserves stand at about $1 billion.³⁵⁹ The city says it avoided "additional use of reserves" to balance FY27.³⁵⁸
• Looking ahead. The Boston Policy Institute projects a shortfall of $1.7 billion to $2.1 billion over five years.³⁵⁹

The council's power over these totals is small. Its FY27 amendments came to $11.8 million, about 0.2% of the budget, and the mayor rejected $1.4 million of them.³⁵⁴

How the federal infrastructure law works

The Infrastructure Investment and Jobs Act (IIJA), enacted in 2021, authorized $1.2 trillion, of which $550 billion was new funding.³⁶⁸ Our reading: the gap between the two figures is mostly spending that was already expected, so the $550 billion is the better measure of what the law added.

Trackers count IIJA dollars in different ways - allocated, announced, obligated and paid out - and the numbers differ a lot. Obligated means legally committed to a specific project, even if no money has been paid yet. Some examples, each measuring something different:

• By September 2024, about $480 billion (40%) had been allocated to projects.³⁶⁸
• For the Department of Transportation's portion only, as of April 30, 2026: enacted budget authority was $567.2 billion ($545.6 billion after adjustments), 70.5% had been obligated, about 89.8% had been announced, and $160.7 billion remained unobligated.³⁶⁹

IIJA program authorities expire on September 30, 2026.³⁷⁰ A bill passed by the Senate Appropriations Committee on August 8, 2026 would extend many of them to December 11, 2026.³⁷⁰ Our sources do not confirm whether that extension became law.

How it changed

• 1980: Massachusetts voters approve Proposition 2½, effective FY1982.³⁶⁵
• 1998: The American Society of Civil Engineers (ASCE) begins its Report Card for America's Infrastructure.³⁷¹
• 2018: Direct central government operating funding for Transport for London ends.³³⁵
• 2021: IIJA enacted.³⁶⁸
• 2025: ASCE gives US infrastructure an overall C.³⁷¹

What does the ASCE report card say?

The ASCE grades US infrastructure in a periodic report card. Its 2025 report card, released March 25, 2025, gave an overall grade of C, up from C- in 2021 and the highest since the report card began in 1998.³⁷¹ It estimates a $3.7 trillion investment gap: the difference between what is needed to reach a good state of repair and what is being spent.³⁷¹ The report covers 18 categories, with broadband added for the first time.³⁷¹

Source for all grades: ASCE.³⁷¹

The ASCE is an engineers' professional society, and its grades are its own assessment.

What's changing now (2026)

Three pressures meet in 2026. Boston's own budget is growing at its slowest rate since FY10 while costs such as health insurance climb.³⁵⁸ The federal infrastructure law's program authority hit its expiry date on September 30, with an extension pending in Congress.³⁷⁰ And the municipal bond market keeps growing, with $473.8 billion issued in the first nine months of the year.³⁶⁶

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18The rules for building in a city

The short version: Before anything gets built in a city, it passes through layers of rules. Zoning decides what may go where - homes, shops, factories, how tall, how dense. Building codes decide how it must be built so it does not fall down, burn or poison anyone. Permits and inspections check that the rules were followed, and before anyone digs into a street, the owners of every buried pipe and cable need to know.

What is the difference between zoning and a building code?

The two get mixed up constantly. In short:

• Zoning answers what and where. It divides a city into districts and sets what uses are allowed in each - housing, offices, industry - along with limits on height, bulk, density, parking and how far a building sits from the lot line.
• A building code answers how. It sets the technical rules for construction: structure, fire safety, exits, plumbing, electrical work and energy use.

A tower can meet every line of the building code and still be illegal because the zoning says that block is for three-story houses. A house can sit in exactly the right zone and still fail inspection because its stairs are too steep. The two systems are usually run by different offices, written by different people and changed in different ways: in the US, zoning is mostly local politics, while building codes are mostly technical documents.

In the US, when a project does not fit the zoning, the owner typically asks for permission to break the rule - a variance - from a local board.

How it changed

New York City's 1916 Zoning Resolution is generally described as the first citywide zoning code in the US.³⁷² It began as a rule on tall buildings, and other cities soon copied its provisions.³⁷³ On November 22, 1926, in Village of Euclid v. Ambler Realty Co., the US Supreme Court upheld comprehensive zoning by a 6-3 vote, giving land-use zones a constitutional footing across the country.³⁷³³⁷⁴

Our reading: zoning and building codes grew out of the same problems the sanitary reformers of the 1800s faced - crowding, fire and disease (see How cities came to need infrastructure). Zoning later took on a second role, shaping who could afford to live where. How much zoning should do is now one of the main arguments over housing, and people across the political spectrum disagree about it.

Zoning and permitting also differ a lot between countries. The US model of fixed districts set out in advance is one approach among several.

England's system, for example, is discretionary: planners and planning committees decide each proposal case by case, rather than settling most questions in a plan drawn up in advance.³⁷⁵ Japan sets zoning nationally, with about a dozen zones; a proposal that complies with the zone and the building regulations must be granted permission.³⁷⁵

Who checks the building?

Building rules are enforced in stages. The usual US sequence for a new building or a major renovation runs roughly like this:

1. Zoning review - does the use and size fit the district, or does it need a variance?
2. Plan review - do the drawings meet the building code?
3. Permits - separate permits for the building and often for plumbing, electrical and gas work.
4. Inspections - inspectors visit at set stages, often before walls are closed up so they can see the wiring and pipes.
5. Certificate of occupancy - an official document confirming the finished building meets the codes and may be used.

The people doing this work - plan examiners, building inspectors, plumbing and electrical inspectors - make judgment calls that affect both safety and how long a project takes. That is one reason the same office can be criticized both for being too slow and for being too lenient.

What happens before someone digs up a street?

A city street is a shared roof over a buried network. Under any given block there may be a water main, a sewer, a storm drain, gas, electric and telecom lines, each owned by a different organization. In Boston alone, one commission runs about 1,015 miles (1,630 km) of water main and 1,435 miles (2,310 km) of sewer and storm drain pipe.⁴⁴ A backhoe that hits a gas line or a fiber trunk can cause an explosion or knock out service to thousands of people.

The practical answer is to tell every utility before digging, so each can mark its lines on the pavement first. The painted lines and small flags on sidewalks are those marks, color-coded by the type of line. In Massachusetts, the Dig Safe Law (G.L. c. 82, ss. 40-40E) requires anyone excavating to contact Dig Safe, by dialing 811, at least 72 business hours ahead; Saturdays, Sundays and holidays do not count.³⁷⁶ The digger first outlines the planned area with white paint or stakes.³⁷⁶

In the US, the colors follow a uniform code from the American Public Works Association (APWA): red for electric, yellow for gas, oil and steam, orange for communications, blue for drinking water, green for sewers and drains, purple for reclaimed water and irrigation, pink for temporary survey marks, and white for the proposed excavation.³⁷⁷

Beyond safety marking, cities also try to coordinate digging, so that the same block is not torn up by the water body in spring, the gas company in summer and the city's repaving crew in the fall. The coordination problem follows from the patchwork of owners described in Who actually runs a city: no single owner has the full picture.

In Boston

Boston's Zoning Code was enacted in 1964 and has been revised many times since.³⁷⁸ When a project does not comply, the Inspectional Services Department (ISD) issues a zoning refusal letter, and the owner then has 45 days to appeal to the Zoning Board of Appeal (ZBA).³⁷⁸ The ZBA can grant variances and conditional use permits; a motion needs five members in favor to pass.³⁷⁸ ISD also issues the building permits - a short form for minor alterations, a long form for new buildings and major work.³⁷⁸

The building code itself is set by the state. The 10th edition of the Massachusetts State Building Code, 780 CMR, is based on modified versions of the 2021 International Codes, including the International Building Code.³⁷⁹ It first took effect on October 11, 2024, and after a concurrency period ending June 30, 2025, it became the only building code in effect.³⁷⁹

Building also feeds the city's finances. Under Proposition 2½, Boston's property tax levy can grow 2.5% a year plus "new growth" from new construction; rising values on existing property do not count.³⁶⁵ Boston already collects the maximum the law allows.³⁴² So for a Massachusetts city, new construction is one of the few ways to grow property tax revenue faster than 2.5% a year, which gives city hall a financial interest in what gets built.

The street-digging side is also tangled in Boston because the main pipe owners are not city departments. BWSC, which owns the local water and sewer mains, is a body created by state law "separate and apart from the City of Boston."⁴⁴ Its pipes connect to the state MWRA's system at 27 metered points.⁴⁴ Any street opening near one of those connections involves at least two public bodies besides the city.

What's changing now (2026)

Energy rules are the fastest-moving part of building codes in Massachusetts, as cities try to cut emissions from new buildings.

Massachusetts municipalities can opt into two state energy codes beyond the default, the "stretch" code and the "specialized" code; as of June 2025, 245 had adopted the stretch code and 55 the specialized code.³⁸⁰ Boston's specialized code took effect on January 1, 2024.³⁸⁰ It requires new buildings and major renovations to follow one of three paths - zero energy, all-electric, or mixed fuel with pre-wiring for electrification and on-site solar where feasible.³⁸¹ Separately, a 2022 state climate law created a fossil-fuel-free demonstration project for 10 municipalities: Arlington, Lexington, Brookline, Acton, Concord, Cambridge, Lincoln, Newton, West Tisbury and Aquinnah. Boston is not among them.³⁸²

Rules for existing buildings - limits on how much carbon large buildings may emit each year - are covered in How cities are adapting to a changing climate.

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19How cities are adapting to a changing climate

The short version: Cities built at the water's edge are planning for seas that are already rising, heavier rain and hotter summers, while also trying to cut the emissions from their own buildings. Boston's 2016 Climate Ready Boston study set its baseline: up to roughly 1.5 feet of sea level rise by 2050 and at least 3 feet after 2070, with today's 1-in-100-year flood becoming a 1-in-10-year flood after mid-century. The responses range from raised parks and flood barriers to rules for building emissions.

How much will sea levels rise in Boston?

The planning numbers come from Climate Ready Boston, a city study released in December 2016.⁴² Secondary reports of it give slightly different ranges, so here is what each says:

• The Barr Foundation's summary: sea level rise of roughly 7 inches to 1.5 feet by 2050 regardless of future emissions, and at least 3 feet after 2070.⁴²
• CommonWealth Beacon's account: a most likely rise of 7.5 to 18 inches by 2050, with a maximum plausible rise of 30 inches; and roughly 3.2 to 7.4 feet by 2100 depending on emissions, with a maximum plausible rise of 10.5 feet.³⁸³
• The Dorchester Reporter's account: 9 inches of rise in the 2030s at Columbia Point and 1.5 feet above 2000 levels by 2050.¹⁰⁰

In metric terms, 1.5 feet is about 46 cm, and 3 feet about 0.9 m. Sea level along coastal New England is rising faster than the global average.³⁸³

The Barr summary describes the 2050 range as holding regardless of future emissions.⁴² The figures after 2070 depend heavily on how much the world emits between now and then.³⁸³

For design, the city uses fixed numbers. Boston's Climate Resilient Design Standards for public rights-of-way plan for 9 inches of sea level rise for structures in place through 2030, 21 inches through 2050, and 40 inches through 2070.³⁸⁴ The 40-inch figure recurs in later city projects: Boston's Resilient Moakley Connectors page, updated in July 2026, describes Moakley Park as a major flood pathway under 40 inches of sea level rise.³⁸⁵

What is a 100-year flood?

A 1% annual-chance flood, often called a "100-year flood," is a flood with a 1-in-100 chance of happening in any given year. The name misleads people: it does not mean once a century, and two can happen in back-to-back years.

Sea level rise changes the odds. Climate Ready Boston found that today's 1% annual-chance waterfront flood would become a 10% annual-chance flood after mid-century.⁴² For scale: over 30 years, a 1% annual chance adds up to roughly a one-in-four chance of at least one such flood. At 10% a year, at least one becomes close to certain, and more than one is likely.

Exposure grows with it. By about 2070, roughly 85,000 people and $85 billion of property would be exposed to flooding.⁴² In Dorchester alone, "as soon as the 2070s," about 4,500 structures could flood in a low-probability event, causing $86 million in direct physical damage.¹⁰⁰

Why not build one big sea wall?

A single barrier across Boston Harbor would likely cost more than $10 billion.¹⁰⁰ Instead, Boston's planning assumes the city "will require multiple layers of flood protection."³⁸³ In practice, that means defending low spots where water would enter, raising parks and roads at those points, and changing how buildings near the water are built, rather than relying on one wall.

The low spots matter because floodwater follows the ground. Land around Moakley Park and Interstate 93 in South Boston is low-lying and creates a path for floodwater toward South Boston, the South End and Roxbury.¹⁰⁰ So a flood barrier at a waterfront park can protect neighborhoods well inland, which helps explain why parks have become flood infrastructure in Boston's plans.

As of fall 2025, the plan for Moakley Park centered on a 2,500-foot landscaped berm meant to protect the park, neighborhoods and evacuation routes, with a state environmental (MEPA) filing expected in October or November 2025.³⁸⁶ A related city project for the areas north and south of the park lists 2026 as its expected completion year and held community meetings in November 2025 and June 2026.³⁸⁵

In East Boston, the city installed a deployable flood barrier on the Mary Ellen Welch Greenway in 2018, a measure first identified in the 2017 Coastal Resilience Solutions report for East Boston and Charlestown; it blocks a surge path under Sumner Street and protects almost 4,300 residents.³⁸⁷ A separate Greenway rebuild is expected to be under construction until about December 2026.³⁸⁷

How it changed

Boston's planning grew out of a design exercise before it became policy. The Boston Living With Water design competition, launched in 2014, drew about 50 entries from seven countries.³⁸³ Teams redesigned real sites to "continue to thrive once sea levels are five feet higher than today."³⁸³ The city also exchanged ideas with experts from Copenhagen, the Netherlands and Hamburg, according to CommonWealth Beacon, which gives no further detail.³⁸³

Climate Ready Boston followed in December 2016.⁴²

Those foreign exchanges point to cities that are often cited as models.

Rotterdam's Benthemplein water square, opened in December 2013, collects rainwater in sunken basins during heavy storms to ease pressure on the sewers; its sunken sports area floods only in extreme rain and dries out for play afterward.³⁸⁸ Copenhagen drew up its Cloudburst Management Plan in 2012 after a 2011 cloudburst caused more than 6 billion Danish kroner in damage. The plan combines a larger sewer network with about 300 surface projects that hold or channel water.³⁸⁹

In the US, New York's East Side Coastal Resiliency project is a $1.45 billion, 2.4-mile flood barrier on Manhattan's Lower East Side, which rebuilds East River Park 8 to 10 feet higher than before.³⁹⁰ Sections opened in stages from 2022 to 2025, and the city expects the full park to reopen in early 2027.³⁹⁰ The project drew strong opposition. In 2020, groups including East River Park Action sued, arguing it would cut the park off from the neighborhood, and a state judge ruled against them. Critics also objected to the loss of more than 1,000 mature trees and the long park closure, and proposed barriers along the FDR Drive instead.³⁹¹

Flooding from the sky, not only the sea

Coastal flooding is one threat. Heavy rain is another, and it hits places nowhere near the shore when storm drains cannot keep up. The ASCE's 2025 report card gave US stormwater infrastructure a D, among the lowest grades of any category.³⁷¹ In Boston, storm drains belong to the Boston Water and Sewer Commission, which runs about 1,435 miles (2,310 km) of sewer and storm drain pipe.⁴⁴ (How that network works is in Where it goes after you flush (or it rains).)

Pipes sized for the rainstorms of past decades can be overwhelmed by heavier downpours, and replacing them street by street is slow and expensive. That is one reason cities are turning to parks, plazas and other surfaces that can hold water for a few hours.

What about heat?

Cities run hotter than the surrounding countryside because pavement and roofs absorb sun and there is less shade and vegetation; this is called the urban heat island effect. Responses usually include tree planting, lighter-colored roofs and pavement, and cooling centers opened to the public during heat waves.

Boston's plan is Heat Resilience Solutions for Boston, released in spring 2022, which sets out 26 citywide strategies and targets five neighborhoods: Chinatown, Dorchester, East Boston, Mattapan and Roxbury.³⁹² When the mayor declares a heat emergency, Boston Centers for Youth & Families (BCYF) community centers open as cooling centers during their normal hours, as in August 2025.³⁹³

Cutting building emissions

Adaptation is half the picture. The other half is cutting emissions. In cold-climate cities, buildings are a natural target, because heating them burns fuel for much of the year. Rules for new buildings are covered in The rules for building in a city.

Boston's main tool for large existing buildings is an ordinance known as BERDO. First passed in May 2013, it originally required large buildings to report their annual energy and water use.³⁹⁴ A 2021 amendment, approved unanimously by the City Council, added emissions limits for non-residential buildings of 20,000 square feet or more and residential buildings with 15 or more units. The limits begin in 2025 or 2030 depending on building size and reach net zero by 2050.³⁹⁴

In Boston

Pulling the verified pieces together for Boston as of October 2026:

What's changing now (2026)

The project updates above show Boston's Moakley Park and East Boston work still in design or construction in 2026. Two pressures covered in Who pays for the city bear on it. US federal infrastructure money is less certain, with the 2021 infrastructure law's program authorities reaching their expiry date on September 30, 2026.³⁷⁰ And Boston's FY27 budget grew at its slowest rate since FY10.³⁵⁸ Our reading: resilience projects compete for the same capital dollars as schools and roads, and both pressures make that competition harder.

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20One Boston block, 24 hours

The short version: This chapter follows one ordinary downtown Boston block through a typical weekday and night, touching nearly every system in the guide along the way. The block is a composite, not a real address, and the clock times in the headings are illustrative: they mark roughly when each kind of work happens, not a record of any particular day. Most of its facts and numbers come from the chapters before it, with a few added sources on the block's daily routine. Sentences without a citation are our own explanation of how the pieces fit.

Before we start: what is on this block?

Our block sits somewhere between Downtown Crossing and the Financial District. It has the equipment the earlier chapters describe: a few streetlights, a signalized corner with a gray controller cabinet, a red fire alarm box, an office tower with a fire department connection on its wall, shops at street level, and, under the pavement, the pipes, vaults and conduits laid out in A city is one machine. It is a few minutes' walk from Summer Street, where the Great Boston Fire began in 1872 and where the first alarm came from Box 52 at Summer and Lincoln streets.³⁰¹

Unless a scene is marked "on a snow emergency night" or "on a rain night," it describes a typical weekday.

3:00 am - The night shift

The signal at our corner is probably flashing. According to a 2020 GBH report, Boston's traffic engineers run four default timing plans (morning, off-peak, evening and overnight), and many of the city's signals flash overnight, when traffic is light.⁴⁷ A few downtown crosswalk buttons that do nothing by day come alive at night: the Boston Globe reported in 2017 that some are inactive in the daytime but work overnight.¹⁹⁴ (More in How traffic lights work.)

A street sweeper may come through. Boston sweeps main, arterial and commercial roads at night all year, while residential streets get daytime sweeping from April through November.²⁹³ A car left in the way can be towed, at $132 plus $35 a day in storage.²⁹³ Night work on city streets is old. In Tudor England, the gong farmers who emptied cesspits were allowed to work only between 9 pm and 5 am, which is why they were also called "nightmen."⁹

Below the street, water use is near its daily low. This is when storage tanks and towers refill, ready for the morning.

A water distribution textbook from College of the Canyons describes the usual pattern: demand is highest in the early morning and evening, with low use midday and overnight, and storage fills when customer demand is low and empties when it is high.³⁹⁵

4:30 am - Trucks before the light

Trash trucks on busy downtown streets tend to come early, while collection crews can still reach the curb ahead of the traffic and the deliveries. Residential trash in Boston is collected by Capitol Waste Services under a city contract, but downtown shops and offices are a different market: the Public Works Department does not manage commercial waste, and businesses hire their own private haulers.⁶⁰ So more than one company's truck may work the same block on the same morning.

The work is dangerous. In 2024, 36 refuse and recycling collectors died on the job in the US, a rate of 37.4 deaths per 100,000 full-time workers, fifth-highest of any occupation.²⁹⁰

Most of Boston's residential trash goes to waste-to-energy plants run by Reworld and WIN Waste Innovations, where it is burned and the heat used to make electricity.⁶⁰ Bags left on the sidewalk overnight are also food for rats. The city's 2024 Rodent Action Plan named Downtown among its hot spots and put prevention ahead of poison: "We can't poison our way out of a problem like this," said Chief of Operations Dion Irish.⁹⁵ (More in Where your trash actually goes.)

Deliveries follow the trash, with trucks using loading zones or the curb lane to unload before the shops open.

In Boston, curbside truck loading zones are for active loading and unloading only, and the Boston Transportation Department must approve and permit them.³⁹⁶ Hours are set street by street: after a pilot, the department and the Mayor's Office of New Urban Mechanics made 7 am to 7 pm loading-zone hours permanent on Cambridge Street between Somerset and Grove Streets in 2016, to cut double parking and keep traffic moving.³⁹⁷

5:30 am - Lights off, trains on

Around dawn, each streetlight on the block switches itself off. Most streetlights use a photocell, a small light sensor on top of the fixture, or an astronomical timer that calculates sunrise.¹⁵⁹ Boston owns about 71,000 streetlights, maintained by the Public Works Street Lighting Division.⁷² By 2022 about 85% were LED,¹⁷⁹ and the city says the conversion cut their energy use by 60%.⁷² A light still burning at noon often has a failed photocell, and unless the system flags the fault itself, someone has to report it. (More in How streetlights work.)

Underground, the first trains of the day start running. Boston's Red and Orange Lines draw 600 volts DC from a third rail, and the Green Line from an overhead wire, fed by 48 traction power substations.⁵¹ On the Red and Orange Lines, cab signals show the operator the allowed speed inside the train.⁵¹ The habit of an early start is as old as the system: the first train through the Tremont Street Subway ran at 6 am on September 1, 1897.⁸⁰

As of 2026, the MBTA says hours vary, but most bus and train service starts around 5 am and ends around 1 am, and there is no overnight train service in Boston.³⁹⁸

A commuter checking a phone sees the next train because the MBTA publishes its schedules as GTFS and its live positions as GTFS-Realtime, a format the T helped develop with Google.⁸⁸ (More in How the subway and the bus actually run.)

7:00 am - Showers, steam and the morning plan

The office tower on our block starts to draw water. The water came from the Quabbin and Wachusett reservoirs and was treated at the Carroll plant in Marlborough with ozone, ultraviolet light and a chloramine residual that keeps working in the pipes.¹⁰⁵ It entered the Boston Water and Sewer Commission's mains at one of 27 metered connections.⁴⁴ Across MWRA's whole system, average demand runs about 200 million gallons a day.¹⁰² Street pressure serves the lower floors; above that, booster pumps push water into pressure zones of about 9 to 10 floors each.¹⁰¹ (More in Why water reaches the 40th floor.)

What goes down the drains heads for Deer Island, which treats an average of about 380 million gallons a day for 43 communities.¹⁴⁰

On a winter morning, some buildings nearby take their heat from steam. Boston and Cambridge's district steam system, run by Vicinity Energy, serves roughly 70 million square feet of buildings.⁵⁵ (More in Gas under the street, and why steam comes out of it.)

At the corner, the controller switches to its morning plan. In GBH's 2020 account, two to three engineers watch the city's signals from the Traffic Management Center on the seventh floor of City Hall during rush hours.⁴⁷ Boston uses pedestrian recall in busy areas, so the walk signal comes up every cycle whether or not anyone presses the button.⁴⁷ On an accessible signal, the button still matters: Boston's specification calls for a locator tone that repeats every second and a button that vibrates during the walk.¹⁹⁷

Buses on nearby streets now take a tapped bank card or phone, a change that began on MBTA buses and trolleys in August 2024.²³⁴

9:30 am - Paint on the sidewalk

On a typical weekday, somewhere downtown, someone is preparing to dig. The first sign is white paint or stakes: in Massachusetts, the excavator must premark the area, then notify Dig Safe at least 72 business hours ahead so every utility with lines below can come and mark them.⁶⁸ The colored marks that follow are each owner's answer to "what is down there?" A Dig Safe ticket is good for 30 days.⁶⁸ (More in Roads, bridges, tunnels and the hole in your street.)

Much of that digging is gas work. Massachusetts utilities are replacing cast-iron and bare-steel mains under the state's Gas System Enhancement Plan, at a cost that reached $3.46 million per mile in 2025.⁷⁹ The 2018 Merrimack Valley explosions, which began during a main replacement, are a major reason crews and regulators now pay close attention to what else is connected to the old pipe.⁷¹

For anyone walking past who smells rotten eggs, the standard advice is clear: natural gas is odorized with mercaptan so leaks can be noticed, and the right move is to leave and call the utility or emergency services from a safe place.¹⁶⁴

11:00 am - A 311 report

A resident notices a pothole at the crosswalk, or a streetlight that stayed on. Boston helped pioneer the modern way to report it. In 2009, the city's Citizens Connect app let a resident photograph a problem, record its location by GPS and get a tracking number to follow the request.⁸⁹ Boston directs streetlight problems to 311.⁷² Behind the app, the Open311 standard lets a request filed in a third-party app land in the same queue as a phone call.⁹¹ The city publishes many of its datasets on Analyze Boston, its open data portal, which launched in 2017 with about 115 of them.³²⁹

The pothole has a history too. Water gets through cracks, freezes into ice lenses that lift the pavement, and leaves voids when it thaws; traffic then breaks the unsupported surface.⁷⁵ (More in 311, the wires under the street, and city data.)

1:00 pm - Someone pulls the box

Our block's red box is part of the oldest network on the street. Boston's fire alarm telegraph went into service in 1852 as the first municipal system of its kind in the world.⁷⁸ As of April 2026, the city kept about 1,250 street boxes and about 1,200 master boxes that connect schools, hospitals and other buildings directly to the fire department; when a box is pulled, its number appears on a computer screen at the alarm office.⁷³ Most box alarms are not fires: a 2013 report put false alarms at roughly 90% of them.³⁰² (More in From fire alarm boxes to 911.)

When an alarm is real, the clock matters. NFPA 1710, a standard many US career departments measure themselves against, sets 80 seconds from alarm to wheels rolling and 240 seconds of travel for the first engine.³¹⁴ On the way, a fire engine can preempt a traffic signal to get an immediate green.⁷⁴ At the office tower, the crew can pump water into the building's standpipes through the Siamese connection on the wall.⁶⁵

The ambulance side is busier. Boston EMS, the city's ambulance service, handled 140,701 clinical incidents in 2024, with a median response of 7.3 minutes to the most urgent calls against a goal of 6.0 minutes.⁹⁶ That averages about 385 incidents a day across the city.

5:30 pm - The evening peak

The signal switches to its evening plan.⁴⁷ Timing plans like this can set up a "green wave" that favors one direction, often outbound in the evening.

On a hot summer evening, this is also the grid's hardest hour. On June 24, 2025, between 5 and 6 pm, at 97°F (36°C), New England's demand reached 26,586 megawatts, the highest in more than a decade, and reserves ran short for more than three hours.⁸⁵ Downtown, that power reaches buildings through underground networks rather than poles.⁴⁶ In each vault, a network protector opens automatically if power would flow backward into a dead feeder.⁷⁷ (More in How electricity gets to your building.)

The trains are full and, in 2026, faster than they were. After the MBTA cleared its last slow zones in 2024, the Orange Line reached its intended 55 mph limit in 2025 and the Red Line hit 50 mph for the first time in decades.²²⁴ A digital signal system replacing the Red Line's analog signals was 70% complete in May 2026.²⁴⁴

As the light fades, the photocells switch the streetlights back on.¹⁵⁹

8:00 pm - On a rain night

On a night of heavy rain, the water on the block has nowhere to go but down. The Boston Water and Sewer Commission's storm drains are part of about 1,435 miles of sewer and storm drain pipe.⁴⁴ In the older parts of the region, combined sewers carry sewage and rain in the same pipe, and when the mix exceeds what the pipes or the plant can handle, it overflows untreated into rivers and the harbor.⁸¹ MWRA's program cut annual overflow volume by more than 2.8 billion gallons between 1987 and 2015.¹²⁴ (More in Where it goes after you flush (or it rains).)

If the rain turns dangerous, phones on the block buzz together. A Wireless Emergency Alert is a cell broadcast from the towers in an area, so no app or sign-up is needed.³¹⁷ In New York, the same storm would double the work of the subway's pumps.⁵² This is also when sweeping pays off: litter left in the gutter washes into the storm drains.

11:00 pm - On a snow emergency night

When the city declares a snow emergency, cars parked on main roads are ticketed and towed so plows can clear them curb to curb, and discounted garage parking opens two hours before the declaration.⁸² Residents can watch the plowing on Boston Snow Stats, which shows plows on duty, miles plowed and salt used.²⁹⁵ One season's Public Works overnight snow removal update counted more than 74,862 tons of salt and nearly 19,000 truckloads of snow removed.⁸³ Space savers are tolerated only during the declared emergency and must be gone 48 hours after it ends, and never in the South End or Bay Village.⁸² (More in Keeping streets clean and open.)

The salt does not stay on the road. In New York, 68% of Con Edison's 2014 manhole events came in January and February, when most road salt goes down, and nearly 90% were caused by failing cable insulation.⁸⁴ If a storm does knock out power, Eversource's restoration follows a published order: safety calls and blocked roads first, then hospitals and water and sewage plants, then the big lines, then single homes.⁴⁸

1:00 am - Overnight work

The busiest repair work avoids the busiest hours. Crews favor nights and weekends because a closed lane or a stopped train disrupts the fewest people then. The MBTA's Track Improvement Program used planned partial shutdowns to clear what had been 233 speed restrictions in September 2023.²⁴²²⁴³

The signal goes back to flash.⁴⁷ The steam keeps flowing, the network protectors stay closed, and the data keeps moving: networks swap internet traffic at the Boston Internet Exchange at One Summer Street, a short walk from our block.⁹⁰

By 3:00 am the block is back where it started. Nothing on it ever fully shuts off: each system has a quiet hour, but rarely the same one.

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21The toolbox

The short version: Two calculators for questions people ask about their own building and their own bin: how much water pressure is left by the time it reaches your floor, and how much trash a household makes in a year by the US average. They use the rules of thumb and national figures cited in this guide; your building engineer and your city have the real numbers.

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22Test yourself

The short version: Fifteen questions drawn from this guide, from easy to surprising. Each answer explains itself and links to the section that covers it.

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23The glossary

The short version: Every term of art in this guide in plain words, searchable and sorted by system. If a word on a water bill, a snow emergency notice or a public works sign stopped you, it should be here.

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24Where to go next

The short version: The best places to keep going, none of them ours: the agencies that publish the real data, the histories that tell the long story, and the tools that show the city working in real time.

25Open questions and known gaps

The short version: What we looked for and could not pin down well enough to print. If you can source any of it, the corrections desk below wants to hear from you.

26Corrections and updates

The short version: This guide will have mistakes in it, and the people who know best are the ones who run these systems every day. If something here is wrong, out of date or missing credit, tell us and we will fix it and log the change below with the date.