502 (MBTA bus)

A branch (Watertown Line)

Company type	Streetcar route
Industry	Public transportation
Founded	1858
Defunct	1969
Fate	Replaced by MBTA bus route 57
Area served	Boston metropolitan area
Products	Streetcar transit service
Owner	Massachusetts Bay Transportation Authority (MBTA)

The A branch, also known as the Watertown Line, was a streetcar route within the Boston metropolitan area, functioning as a subsidiary line of the Massachusetts Bay Transportation Authority (MBTA) Green Line. Its path extended from Watertown through Newton Corner, Brighton, and Allston, terminating at Kenmore Square. From there, it proceeded via the Boylston Street and Tremont Street subways to reach Park Street station.

Segments of this line trace back to horse-drawn streetcar services established between 1858 and 1880. The stretch connecting Union Square to Oak Square was electrified in 1889 as part of the Beacon Street line (now the Green Line C branch). By 1896, electric streetcars linked Newton Corner with downtown Boston through Brighton and Watertown. Service in Brighton was extended to Watertown by 1912. The line remained operational until 1969, after which MBTA bus route 57 took over its function. However, the tracks continued to be used for non-revenue transfers to Watertown Yard until 1994.

Origins

The Brighton Horse Railroad, a horsecar street railway, commenced construction in 1858. This route began at Central Square in Cambridge, crossed the Charles River into Allston, and proceeded through Union Square along Cambridge Street and Washington Street to Oak Square in Brighton. Managed by the Union Street Railway—a holding company overseeing the Cambridge Railroad system—the line officially opened on November 15, 1858, following resolution of conflicts related to crossing Boston and Worcester Railroad tracks. Service frequency doubled in April 1878, offering cars every 30 minutes. In 1880, a second route connecting Brighton and Cambridge via Market Street and Western Avenue began operation. Although plans existed to extend from Oak Square to Nonantum Square at that time, this extension was not realized; nonetheless, a separate line connected Watertown with Nonantum Square.

During the late 1880s, the West End Street Railway consolidated several horsecar lines including those operated by the Cambridge Railroad. On January 3, 1889, it launched its first electric streetcar service running from the Allston Carhouse near Union Square to Park Square, traveling along Harvard Street, Beacon Street, Massachusetts Avenue, and Boylston Street. Electric operation reached Oak Square by January 13. Electric service between Watertown and Mount Auburn commenced on December 12, 1893; double-tracking was implemented later in that decade. On August 18, 1896, the Western Avenue line became double-tracked and electrified—the final route over the West Boston Bridge to adopt electric traction; prior to this change, horses pulled cars to Central Square before electric service continued into Boston.

Tracks extending eastward from Union Square along North Beacon Street and Commonwealth Avenue to Kenmore Square were inaugurated on May 18, 1896, connecting with existing Beacon Street tracks. By June 13 of that year, the western terminus had been pushed near Newton Corner (Nonantum Square). Starting November 8, 1897, Newton service via Commonwealth Avenue began utilizing the Tremont Street subway. A route linking Nonantum Square with City Point via Allston and Coolidge Corner opened on August 4, 1900. Service was further extended northward to Watertown on December 9, 1912. The line also supported freight transportation during the early decades of the twentieth century.

The Boylston Street subway reached an incline at Kenmore Square on October 3, 1914; immediately thereafter, Watertown-bound streetcars traveling via Brighton Center were routed into this tunnel. Mid-1915 saw the introduction of high-capacity center-entrance streetcars as trailers on this line. Evening peak short-turn trips terminating at Oak Square were lengthened to reach Watertown starting February 23, 1922. The Blandford Street portal on Commonwealth Avenue just west of Kenmore opened on October 23, 1932—marking the final alteration to this route’s alignment. In 1941, this line became Boston’s first predominantly operated by PCC streetcars, replacing earlier Type 4 and Type 5 vehicles.

North Beacon Street line

In June 1894, the West End petitioned the city to authorize construction of a streetcar line along North Beacon Street, stretching from Union Square to the Watertown boundary. Shortly thereafter, the Newtonville and Watertown Street Railway obtained permission to build the segment between and Union Square, intending to utilize West End tracks for access to downtown Boston. Despite opposition from West End, approval was granted by the Watertown Arsenal in 1896, leading to the line’s completion in 1898.

After operational conflicts arose between its parent company, the Newton and Boston Street Railway, and the BERy, service on the line commenced in 1900. On November 18 of that year, through service linking Watertown with the Tremont Street subway was launched as an extension of the Newton-Brighton route. The BERy took ownership of the line in 1907. A distinctive feature was that the portion west of Market Street remained single-tracked, which was uncommon for BERy-operated lines.

The Newton Street Railway, later known as the Middlesex and Boston Street Railway, introduced Waltham–Park Street service via North Beacon Street on February 23, 1903. This route was diverted to Central Square in 1912, moving away from North Beacon Street. Over time, Oak Square–Boston service also diminished, while Watertown–Park Street operations continued. Following the opening of the Boylston Street subway in October 1914, service on North Beacon Street was truncated to a shuttle running between Watertown and Union Square; by June 1917, it had been further reduced to a shuttle connecting Brighton and Watertown.

Bus service replaced the North Beacon Street shuttle on February 23, 1922. A short-lived Watertown–Arsenal Street bus operated during 1925–26. In December 1925, the Central Square–Union Square streetcar route was altered to a new bus line running along River Street; this bus extended to Union Square by September 1926, fully supplanting the streetcar. These two bus routes were consolidated in February 1933 to eliminate transfers—a combined service that persists today as the route 64 bus.

Closure

Prior to 1967, what became known as the Watertown Line carried route number 69; meanwhile, route number 57 originally designated short-turn trips on Huntington Avenue. The northernmost Green Line branch carried the letter "A." Turnback loops were located at Union Square, Oak Square, and Watertown terminal, with an additional loop at Braves Field (1915–1962) facilitating event-related service on Commonwealth Avenue.

The inauguration of the Riverside Line in 1959 resulted in PCC streetcars being reassigned from Cambridge to Riverside. However, maintenance difficulties increased due to an aging fleet mainly composed of 1940s-era PCC cars and a complex vehicle mix. By the late 1960s, a shortage of Green Line streetcars caused by wear and insufficient replacements led the MBTA to propose a "trial" suspension of the A branch.

Extensive street-running sections made this branch a candidate for closure alongside prior resistance against extending service beyond Newton Corner. Streetcar operations ended on June 20, 1969; bus route 57 commenced service immediately afterward.

Track removal

Following discontinuation in 1969, tracks remained intact to permit Green Line streetcars access to Watertown Carhouse for maintenance purposes. The final use occurred in 1993 during refurbishment work on PCC cars destined for the Ashmont–Mattapan High-Speed Line. Overhead electrification wires were dismantled in March 1994.

By summer 1996, most overhead equipment and track infrastructure were removed during resurfacing of North Beacon Street. Some track segments survive at Watertown Yard bus terminal and as a short remaining stub at Packard's Corner—previously utilized for storing disabled trains until it was shortened in the mid-2000s; its switch was disconnected in 2014 and paved over by 2020.

Proposals to reinstate direct downtown Boston service along this northern corridor without requiring transfers at Kenmore were considered but ultimately rejected due to high costs and safety concerns compared with current bus alternatives.

Route 57

The 57 Watertown Yard–Kenmore station bus service originated in 1969, taking over from the former A branch streetcar line. It largely follows the same path, except at the Newton Corner rotary where inbound buses adhere to regular traffic flow instead of using a counterflow lane. Initially operating as limited-stop service between Packards Corner and Kenmore, the 57 began stopping locally along Commonwealth Avenue in December 2006 to boost passenger numbers.

Following the elimination of free transfers in 1961, riders from Watertown were required to pay double fares downtown until January 1, 2007, when free transfers were reinstated for CharlieCard holders.

Short-turn trips between Oak Square and Kenmore were discontinued in 1971 but partially reinstated in 1987 and again in 1999. In September 2008, a dedicated 57A Oak Square–Kenmore short-turn service was introduced during weekday peak periods to alleviate crowding. The 57A handled roughly half of rush-hour trips, with off-peak buses covering the entire route. Except for a few school-day trips, Oak Square short-turn service ended in December 2020 as full-route frequencies were increased.

Route 57 remains a vital MBTA bus corridor, maintaining headways of 10 to 12 minutes throughout the day. By 2012, the combined ridership of routes 57 and 57A ranked ninth across the system, with over 10,000 boardings on weekdays. Weekday operations are based out of Albany Street Garage, while evening and weekend services operate from Cabot Garage. Additionally, an early-morning trip to , designated internally as route 191, runs primarily for MBTA employees but is open to public riders.

A review conducted by the MBTA in 2018–19 highlighted overcrowding during peak times and reliability challenges on route 57 but did not recommend immediate adjustments. The 2022 comprehensive bus network redesign proposed increasing service frequency to at least every 15 minutes throughout all operating hours. The 57A short-turn was reintroduced in December 2024 but was discontinued again by April 2025.

Express buses

West of Brighton Center, two express routes provide service to downtown Boston via Copley Square:

• 501 Brighton Center–Federal Street & Franklin Street
• 504 Watertown Yard–Federal Street & Franklin Street

Express bus service from Brighton and Watertown dates back to the "A" branch period. The original express route, numbered 61 Watertown/Newton Corner-Downtown Boston, began operations in July 1967 and underwent several renumberings during the late 1960s and early 1970s to reflect changes in express routing. By June 1970, express routes were assigned numbers in the 300-series (including routes 304, 301, and 302). Minor modifications to downtown routing took place throughout the late 1970s and into the 1980s. Midday and Saturday service on route 302 commenced in January 1983; by December 1989 these trips were extended to include a Copley Square stop under route number 304. In September 1996, these routes were renumbered once more to their current designations: 501, 502, and 504. The addition of route 503 occurred in January 2005.

The MBTA’s system review during 2018–19 identified problems with routes 501 and 503 such as closely spaced stops and irregular afternoon schedules; however, routes 502 and 504 did not exhibit significant issues. To improve efficiency, outbound stops at Newton Corner for routes 502 and 504 were consolidated starting September 2019; concurrently, outbound trips on routes 501 and 503 began serving Newton Corner stops.

During the COVID-19 pandemic starting March 17, 2020, most MBTA services operated on Saturday schedules. Weekday-only routes like the 502 and 503 were suspended while routes 501 and 504 ran on reduced timetables. Route 504 adjusted its service pattern to replace route 502 via Copley Square and resumed looping outbound through Newton Corner. Route 501 was suspended from June through August of that year; upon resumption it included stops at Copley Square.

Proposals released in May 2022 sought to make these pandemic-related changes permanent by restricting routes 501 and 504 to weekday peak hours only. However, a November 2022 update restored midday service on route 504.

External links

• A visual comparison of Allston's streetcars and their present-day locations provided by Boston.com through the Wayback Machine