503 (MBTA bus)
| 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 service |
The A branch, also known as the Watertown Line, was a streetcar route serving the Boston metropolitan area as a branch 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 continued via the Boylston Street and Tremont Street subways to reach Park Street station.
Segments of this route originally operated as horse-drawn streetcar lines between 1858 and 1880. The stretch connecting Union Square to Oak Square was electrified in 1889 and became part of the Green Line’s C branch (Beacon Street line). By 1896, electric streetcars linked Newton Corner (Nonantum Square) with downtown Boston through Brighton and Watertown. Service to Brighton was extended further to Watertown in 1912. The line remained operational until 1969, when it was replaced by MBTA bus route 57; however, non-revenue trips to Watertown Yard continued until 1994.
Formation
The Brighton Horse Railroad, a horsecar street railway, began construction in 1858. Starting at Central Square in Cambridge, the line crossed the Charles River into Allston before proceeding through Union Square to Oak Square in Brighton. Managed by the Union Street Railway—a holding company for the Cambridge Railroad system—it commenced service on November 15, 1858, following resolution of disputes over track crossings. By April 1878, service frequency increased to cars every thirty minutes. In 1880, a second route connecting Brighton and Cambridge via Market Street and Western Avenue was inaugurated. Although an extension from Oak Square to Nonantum Square was proposed but never completed, a separate line linking Watertown to Nonantum Square did exist.
During the late 1880s, the West End Street Railway consolidated various horsecar lines including those of the Cambridge Railroad. On January 3, 1889, it launched its inaugural electric streetcar service between Allston Carhouse (just north of Union Square) and Park Square, traveling along Harvard Street, Beacon Street, Massachusetts Avenue, and Boylston Street; electric operations were extended to Oak Square by January 13. Electric service connecting Watertown and Mount Auburn began on December 12, 1893, with double tracking added later that decade. On August 18, 1896, the Western Avenue line became double-tracked and electrified—the final West Boston Bridge line converted from horse-drawn cars.
Tracks extending eastward from Union Square along North Beacon Street and Commonwealth Avenue to Kenmore Square opened on May 18, 1896, linking with existing Beacon Street tracks. By June 13, the western terminus had reached just short of Newton Corner (Nonantum Square). Service from Newton via Commonwealth Avenue started operating into the Tremont Street subway on November 8, 1897. A lengthy route from Nonantum Square to City Point via Allston and Coolidge Corner commenced on August 4, 1900. In December 1912, service was extended northward to Watertown utilizing existing tracks along Galen Street. During the early twentieth century, this line also carried freight.
The Boylston Street subway opened up to the Kenmore Square incline on October 3, 1914; Watertown-bound service via Brighton Center was immediately routed through it. Mid-1915 saw the introduction of high-capacity center-entrance streetcars as trailers on this line. Evening peak short-turn trips from Oak Square were extended to Watertown starting February 23, 1922. The Blandford Street portal on Commonwealth Avenue west of Kenmore opened on October 23, 1932—marking the final routing change for this service. In 1941, this route became Boston’s first primary PCC streetcar line, replacing older vehicle models.
North Beacon Street line
In June 1894, the West End requested municipal permission to construct a streetcar line along North Beacon Street, spanning from Union Square to the Watertown boundary. Shortly thereafter, the Newtonville and Watertown Street Railway obtained authorization to build the section between and Union Square, planning to utilize West End tracks for access to downtown Boston. Despite objections from West End, approval was granted by the Watertown Arsenal in 1896, leading to the line's construction in 1898.
The line officially commenced service in 1900 following operational disagreements between its parent company, the Newton and Boston Street Railway, and BERy. Starting November 18, 1900, through service operated between Watertown and the Tremont Street subway as a branch of the Newton-Brighton route. In 1907, BERy purchased the line from Newton and Boston. A distinctive feature was that the portion west of Market Street remained single-tracked, an uncommon characteristic among BERy routes.
Service between Waltham and Park Street via North Beacon Street was initiated by the Newton Street Railway (later renamed Middlesex and Boston Street Railway) on February 23, 1903. This route was redirected to Central Square in 1912, with Oak Square–Boston service similarly shortened. Watertown–Park Street operations along North Beacon Street continued until October 1914; after the Boylston Street subway opened, service was reduced to a shuttle running between Watertown and Union Square. By June 1917, this shuttle was further limited to operate only between Brighton/Watertown bridge and Union Square.
On February 23, 1922, bus service replaced the North Beacon Street shuttle. A brief bus route connecting Watertown and Arsenal Street bridge ran during 1925–26. In December 1925, the Central Square–Union Square line was rerouted through Western Avenue and Soldiers Field Road; subsequently, a new bus route on River Street was extended to Union Square in September 1926, supplanting streetcar operations. These routes merged in February 1933 to provide continuous service without transfers—a pattern that continues today as the route 64 bus.
Closure
Prior to 1967, what became known as the Watertown Line operated under route number 69; meanwhile, route number 57 originally designated short-turn services on the Huntington Avenue line terminating at Heath Street. The northernmost branch of the Green Line was identified by the letter "A." Turnback loops were established at Union Square, Oak Square, and the Watertown terminal; additionally, a loop at Braves Field was active from 1915 until 1962 for event-related services.
The Riverside Line’s inauguration in 1959 prompted reassignment of PCC streetcars to that corridor; however, maintenance challenges arose due to an aging fleet from the 1940s combined with a diverse vehicle mix. By the late 1960s, shortages in available streetcars compelled the MBTA to announce a provisional closure of the A branch.
The A branch was chosen for discontinuation because of its extensive street-running segment between Watertown and Packards Corner and prior resistance to extending service beyond Newton Corner. Streetcar operations ended on June 20, 1969; bus service under route number 57 commenced immediately afterward.
Track removal
Following closure, tracks remained intact for multiple decades to facilitate access to Watertown Carhouse for maintenance purposes. The last recorded use occurred in 1993 when PCC streetcars destined for the Ashmont–Mattapan Line underwent refurbishment there. Overhead trolley wires were dismantled by March 1994.
By summer 1996, most track infrastructure and overhead wiring had been removed during resurfacing work on North Beacon Street. Some track sections persist at Watertown Yard bus terminal and as a short stub at Packard's Corner—the original divergence point from the B branch. This stub served as storage for disabled trains until it was shortened in the mid-2000s; its switch was disconnected in 2014 and eventually paved over by 2020.
Proposals to restore direct downtown service along this northern corridor—eliminating transfers at Kenmore—were evaluated but ultimately rejected due to high costs and safety concerns compared with existing bus alternatives.
Route 57
The 57 Watertown Yard–Kenmore station bus route originated in 1969 as a substitute for the A branch streetcar line. It largely follows the historic path, although inbound buses now utilize traffic lanes at the Newton Corner rotary instead of a dedicated counterflow lane. Initially introduced as a limited-stop service between Packards Corner and Kenmore to complement the "B" branch local service, the 57 expanded to include local stops along Commonwealth Avenue starting December 2006.
Before 2007, passengers traveling from Watertown faced double fares due to the removal of free transfers following the bustitution; this issue was addressed with a revised fare policy effective January 1, 2007, which reinstated free transfers via CharlieCard.
Rush hour short-turn trips between Oak Square and Kenmore were discontinued in 1971 but were partially reinstated later. In September 2008, the MBTA launched the 57A Oak Square–Kenmore short-turn service during weekday peak periods to reduce crowding; about half of the rush hour trips operated as 57A. This Oak Square short-turn service was eliminated in December 2020 except for a few school-day trips, accompanied by an increase in full-route frequency.
Route 57 remains a vital MBTA bus corridor with frequencies of 10 to 12 minutes throughout the day. As of 2012, combined ridership for routes 57 and 57A ranked ninth highest across the MBTA system, with over 10,000 boardings on weekdays. The route is dispatched from Albany Street Bus Facility during weekday rush and midday periods, shifting operations to Cabot Garage during evenings, weekends, and holidays. An early morning trip designated internally as route 191 operates primarily for MBTA staff but is open to all riders.
A system review conducted by MBTA in 2018–19 noted challenges with peak overcrowding and reliability on route 57 but did not implement immediate modifications. The proposed bus network redesign in 2022 recommended boosting frequency to at least every 15 minutes throughout all operating hours. The 57A short-turn service was briefly reintroduced in December 2024 but discontinued again by April 2025.
Express buses
Two express routes provide service between areas west of Brighton Center and downtown Boston via Copley Square:
- 501 Brighton Center–Federal Street & Franklin Street
- 504 Watertown Yard–Federal Street & Franklin Street
Express transit connecting Brighton and Watertown to downtown dates back to the "A" branch streetcar era. The initial route, numbered 61 and running from Watertown/Newton Corner to Downtown, began operations in July 1967. Throughout the 1970s, this route underwent several renumberings reflecting adjustments and express status changes. By September 1996, these services had evolved into routes 501, 502, and 504. Route 503 was introduced later in January 2005.
The MBTA’s review during 2018–19 identified concerns with routes 501 and 503 involving closely spaced stops and inconsistent afternoon schedules, while routes 502 and 504 were found to operate without significant issues. To enhance operational efficiency, outbound trips on routes 502 and 504 were rerouted in September 2019 to avoid the Newton Corner rotary; simultaneously, outbound routes 501 and 503 began serving stops at Newton Corner.
Service reductions triggered by the COVID-19 pandemic commenced in March 2020: routes 502 and 503 were suspended; meanwhile, routes 501 and 504 ran on reduced schedules with route 504 assuming route 502’s service through Copley Square. Route 501 was temporarily suspended between June and August of that year before resuming service including Copley Square stops. Proposed adjustments in May 2022 made these changes permanent, restricting routes 501 and 504 to weekday peak hours; however, midday service on route 504 was restored in November 2022.