Massachusetts Bay Transportation Authority bus system| Company type | Public transit agency |
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| Industry | Public transportation |
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| Predecessor | Boston Elevated Railway, Eastern Massachusetts Street Railway, Middlesex and Boston Street Railway |
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| Founded | 1964 |
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| Headquarters | Boston , United States |
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Area served | Boston metropolitan region, Massachusetts |
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| Products | Bus services including local routes, express routes, Silver Line BRT |
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| Owner | Massachusetts Bay Transportation Authority (MBTA) |
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| Website | www.mbta.com/bus |
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The Massachusetts Bay Transportation Authority bus system manages 151 routes throughout the Boston, Massachusetts metropolitan region. Each route provides connections to the MBTA subway, MBTA Commuter Rail, or other MBTA bus lines. Many of these services trace their origins back to the streetcar networks formerly operated by the Boston Elevated Railway and suburban operators such as the Eastern Massachusetts Street Railway and Middlesex and Boston Street Railway. Out of the total routes, 147 are directly operated by the MBTA, while four are managed by private contractors. Additionally, four suburban routes benefit from partial MBTA financial support.
The majority of bus routes require a local fare payment, set at $1.70 for a one-way trip as of 2024. The Silver Line waterfront routes (SL1, SL2, SL3, SLW) apply the subway fare of $2.40. Express buses incorporate a two-tiered fare structure: a local segment charged at the standard local fare and an express highway segment with an increased fare of $4.25.
During the COVID-19 pandemic, service levels were curtailed or modified but had largely resumed to pre-pandemic standards by 2021, although certain routes remain inactive. Since 2018, the MBTA has been undertaking an extensive redesign of its bus network, aiming for completion by 2028. The initial phase was implemented in December 2024.
Silver Line
The Silver Line represents a six-route bus rapid transit system promoted as rapid transit service. It consists of two distinct branches: the Waterfront service (routes SL1, SL2, SL3, and the rush-hour SLW shuttle), which operates through the South Boston Transitway tunnel; and the Washington Street service (routes SL4 and SL5), which runs along surface streets. Waterfront routes require payment of subway fares, whereas Washington Street routes charge local bus fares. All Silver Line vehicles are articulated buses; those on the Waterfront routes are hybrids equipped with extended battery capacity to enable electric operation within tunnels.
Route SL5 replaced the former Washington Street Elevated line in 2002. The Shuttle service commenced in 2004, followed by the introduction of SL2 and the original SL3 also in 2004, and SL1 in 2005 utilizing dual-mode buses. The SL4 route was launched in 2009 as a substitute for a canceled tunnel project. A new SL3 route extending to Chelsea began service in 2018.
Crosstown
The MBTA operates two crosstown (CT) routes that provide limited-stop connections between major subway stations and key bus transfer locations. Originally launched with three crosstown routes in 1994, route CT1 was merged into route 1 in 2019.
1–121
These routes cover nearly all local transit within Boston’s central metropolitan region, with many tracing their origins to former Boston Elevated Railway streetcar corridors. Arranged approximately in a clockwise manner from the southeast to the northeast, this network has maintained consistent structure since the BERy period, evolving through the Metropolitan Transit Authority starting in 1947 and later transitioning to the MBTA in 1964. Some smaller lines have been consolidated into main trunk routes, while additional services were introduced during both the M.T.A. and MBTA administrations.
A group of seven routes—, , , , , , and —serve the outer western suburbs such as Bedford, Waltham, Lexington, and Needham. These lines descend from Middlesex and Boston Street Railway routes that were incorporated into the system in 1972.
In 2004, fourteen routes—, , , , , , , , , , , , , and —were identified as key bus routes. These high-demand corridors complement subway service by offering frequent connections within Boston’s most densely populated neighborhoods. Beginning with the MBTA's Bus Network Redesign in 2024, the term "key bus route" is being phased out in favor of a more inclusive frequent route network. Notably, routes 28 and 39 operate with 60-foot articulated buses.
There are four early morning round trips running between peripheral stations and over sections of multiple local routes. Though primarily intended for station agents, these trips are accessible to all passengers. Internally numbered 191–194, they are displayed as variants of regular local routes.
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131–137
Routes numbered 131 through 137 serve the Melrose vicinity and originate from former Eastern Massachusetts Street Railway lines that became part of the MBTA network in 1968. Routes 136 (now discontinued) and 137 once extended briefly to Lowell and Lawrence while under MBTA management. Route 132 was originally operated by Service Bus Lines before transitioning to MBTA control in 1975.
171
Route 171 offers limited service as a replacement for early morning CT3 runs that were shortened from Logan Airport in 2002. Other routes in the 170 series were brief industrial shuttle services.
201–202
Originally formed in 1962 by the M.T.A. from BERY's 20 and 21 stubs, the 20 belt route was renumbered in 2005 as routes 201 and 202 to better indicate the direction of each loop.
210–245
Operating primarily in Quincy, Massachusetts, routes numbered 210 through 245 trace their origins to former Eastern Massachusetts Street Railway lines, which were integrated into the MBTA system in 1968. After the gradual launch of the Red Line's Braintree Branch during the 1970s and 1980s, these routes were adjusted to connect with rapid transit stations, predominantly terminating at .
350–354
Covering areas including Burlington and Woburn, these routes originated from the Eastern Massachusetts Street Railway's Lowell–Boston line, which was acquired by the MBTA in 1968 and subsequently shortened to terminate at Burlington.
411–465
Serving Lynn and the North Shore region, these routes incorporate former Service Bus Lines routes (411 and 430, integrated in 1975) as well as Eastern Massachusetts Street Railway routes (acquired in 1968). On weekends, shortened versions of these routes, marked with a W suffix, conclude at Wonderland instead of Haymarket.
501–558
These express services provide transit between Newton, Massachusetts and downtown Boston via the Massachusetts Turnpike (I-90). The MBTA introduced the 500 series during the 1960s to utilize the newly extended turnpike access into Boston. The 550 series originated from Middlesex and Boston Street Railway lines serving Newton Corner station, which were extended downtown in the 1960s and later incorporated into the MBTA system in 1972; however, they were truncated back to Newton Corner in 2020.
Privately operated routes
The MBTA provides partial funding for certain suburban bus lines located beyond its primary service boundaries, which connect to various MBTA transit options. Routes 712 through 716 were originally operated by private companies before being incorporated into the MBTA system—specifically, Rapid Transit Inc. managed routes 712 and 713, Nantasket Transportation operated route 714, and Hudson Bus Lines ran route 716.
Routes without assigned numbers function as local circulators initiated by municipalities and receive limited financial support from the MBTA. These services are mostly run by private contractors, with the exception of the Beverly Shuttle, which is overseen by the Cape Ann Transportation Authority.
