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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