MBTA key bus routes

Massachusetts Bay Transportation Authority Primary Bus Routes

Company type	Transit service category
Industry	Public transportation
Founded	2004
Headquarters	Boston , United States
Area served	Boston metropolitan area
Products	Bus transit services

Primary bus routes within the Massachusetts Bay Transportation Authority (MBTA) network referred to the 15 routes distinguished by the highest ridership volumes and frequency benchmarks as outlined in the 2004 MBTA Service Policy. Collectively, these routes comprised roughly 40% of the MBTA's total bus passenger usage. They delivered vital coverage across Boston’s most densely populated neighborhoods and facilitated connections to other MBTA transit modes, thereby enhancing regional mobility.

Identified as a core component of the MBTA’s transit framework, these primary bus routes were featured on updated transit maps displayed at subway stations and public venues, alongside rapid transit and commuter rail services. Recognized as a separate category for targeted service enhancements—including experimental late-night operations—these heavily utilized routes have played a pivotal role in urban transit planning and transportation system analyses. With the implementation of the 2024 Bus Network Redesign, the designation of primary bus routes is being phased out in favor of a broader high-frequency route classification.

History

In November 2006, the MBTA initiated an effort aimed at elevating service quality on its primary bus routes. The 2008 Service Plan advocated for improvements across multiple lines, recommending Route 31 be upgraded to meet primary route criteria. Subsequently, a $10 million Key Routes Improvement Project was launched, funded in part by the American Recovery and Reinvestment Act of 2009. Although initially included, the Silver Line was later separated into its own enhancement initiative. This original improvement program concluded in 2013; however, some proposed upgrades were not fully realized. Notably, primary routes have consistently demonstrated superior service reliability compared to other lines, achieving on-time performance rates of 75% versus 61% as recorded in June 2017.

Research conducted in 2012 revealed that areas adjacent to primary bus routes experienced lower taxicab trip generation rates, suggesting these frequent-service routes effectively attract riders who might otherwise choose taxis.

In April 2014, extended late-night operations on both primary bus and rapid transit lines were introduced on a trial basis for one year, contingent upon ridership levels and sponsorship support. By April 2015, these extended hours were curtailed with some services discontinued entirely; ultimately, late-night service ceased altogether in March 2016.

Primary bus routes were integral to Boston Mayor Marty Walsh’s "Go Boston 2030" vision, which aimed for every household to be located within a ten-minute walk of either a T station or a primary route stop. This plan included proposing a new primary route linking the Longwood Medical Area with JFK/UMass via Roxbury.

In May 2022, the MBTA unveiled a draft Bus Network Redesign plan suggesting modifications to most primary routes while elevating select others into a high-frequency network designed to complement rapid transit services. An updated version of this plan was issued in November 2022.

Criteria for Primary Routes

According to the MBTA’s Service Delivery Policy, Primary Bus Routes are identified based on five key factors:

• Elevated ridership demand
• Integration within the overall system
• Extensive geographic coverage
• Support for significant new developments
• Operation as bus rapid transit

Service Standards

Primary routes are held to more stringent standards than local routes regarding service span and frequency. The following tables illustrate these minimum requirements:

Route Category	Minimum Service Span
Local	Weekdays	7:00 AM – 6:30 PM
	Saturdays	8:00 AM – 6:30 PM
	Sundays	10:00 AM – 6:30 PM
Primary	Weekdays	6:00 AM – Midnight
	Saturdays	6:00 AM – Midnight
	Sundays	7:00 AM – Midnight

Route Category	Minimum Service Frequency
Local	Peak periods (AM & PM)	Every 30 minutes
	Off-peak times	Every 60 minutes
	Weekends	Every 60 minutes
Primary	Peak periods (AM & PM)	Every 10 minutes
	Midday hours	Every 15 minutes
	Evenings and weekends	Every 20 minutes

Route list

The MBTA has identified 15 primary bus routes: 1, 15, 22, 23, 28, 32, 39, 57, 66, 71, 73, 77, 111, 116, and 117. These lines are prioritized for enhancements such as limited-stop or express services, as requested by elected representatives and community members to improve transit effectiveness and capacity.

1

The 1 Harvard Square–Nubian Station line links Cambridge with Roxbury. It originated in September 1962 through the consolidation of two routes that previously split at Massachusetts Avenue: the 76 Harvard–Massachusetts station and the former 47 Massachusetts station–Dudley route. In May 1987, this route was realigned from Washington Street southeastward along Albany Street and Melnea Cass Boulevard to provide service to Boston Medical Center. Currently, it primarily travels along Massachusetts Avenue, beginning at Harvard, passing the Massachusetts Institute of Technology, crossing the Charles River via the Harvard Bridge, entering Boston near the Berklee College of Music, continuing to Boston Medical Center, and then heading southwest to Nubian station via Albany Street and Melnea Cass Boulevard.

In 2015, Cambridge planned to implement signal priority at select intersections for route 1 to enhance operational efficiency. No modifications to this route were included in the May or November 2022 network proposals.

According to Transitmatters' October 2023 assessment, the number 1 bus was identified as the slowest and most prone to bunching within the MBTA system, averaging a speed of just 6.55 mph and exhibiting a bunching rate of 17.7%, reflecting considerable challenges in maintaining reliable service.

15

The 15 Fields Corner Station or St. Peter's Square–Ruggles Station line operates from St. Peter's Square in northern Dorchester northward along Bowdoin Street, then west on Hancock Street, and north on Columbia Street reaching Uphams Corner. From there, it continues west on Dudley Street to Nubian station, proceeds west along Malcolm X Boulevard to , and then heads north on Tremont Street toward Ruggles station. Nighttime and weekend services end at Fields Corner station, traveling via Geneva Avenue and Bowdoin Street back to St. Peter's Square.

This route began bus service on April 6, 1962, replacing the previous trackless trolley operation known as the 15 Kane Square–Dudley via Uphams Corner and Dudley Street. Following the Orange Line’s shift to the Southwest Corridor in May 1987, the route was extended to reach Ruggles. On August 25, 2024, Kane Square service was further extended slightly to St. Peter's Square.

The May 2022 draft network plan suggested extending this route westward to Oak Square, absorbing route , thereby creating an Oak Square–Fields Corner corridor. However, by November 2022, the proposal was revised to truncate the line back at Ruggles, leaving route 65 as a separate service.

22

The 22 Ashmont Station–Ruggles Station via Talbot Ave route begins at Ashmont and proceeds northwest toward the former location of Egleston station. It then travels north along Columbus Avenue and Tremont Street, running adjacent to the Orange Line before terminating at Ruggles.

On April 6, 1962, buses replaced the trackless trolleys on this line, operating under the designation 22 Ashmont–Dudley via Talbot and Warren. Unlike the current alignment, the route continued further north along Warren Street to . In May 1987, following the Orange Line's relocation, service was extended to Ruggles. Proposals in the May and November 2022 network plans suggested altering the inner terminal to Longwood Medical Area.

23

The 23 Ashmont Station–Ruggles Station via Washington Street shares its endpoints with route 22 but follows an alternate course. Departing from Ashmont along Talbot Avenue, it turns north onto Washington Street, then proceeds onto Warren Street reaching Nubian station. From Nubian, it heads west along Malcolm X Boulevard to Roxbury Crossing, before continuing north on Tremont Street to arrive at Ruggles station.

Trackless trolleys were replaced by buses on April 7, 1962, for what was then the 22 Ashmont–Dudley via Washington Street and Warren route. The extension to Ruggles occurred in May 1987 concurrent with the Orange Line’s relocation.

A 2017 analysis identified overcrowding concerns on routes 23 and 28 that could be mitigated by lengthening route 29 and increasing its service frequency. Starting March 1, 2022, a city-funded initiative provides fare-free travel on routes 23, 28, and 29 through February 28, 2026. The May and November 2022 network proposals did not recommend any modifications for route 23.

28

The 28 Mattapan Station–Ruggles Station line serves the neighborhoods of Grove Hall and Mattapan along Blue Hill Avenue, a principal arterial road. Historically, Blue Hill Avenue functioned as a heavily trafficked corridor; in 1945, route 29 Mattapan–Egleston operated with headways as short as 1.5 minutes during morning peak periods. Streetcars ran along this corridor until buses replaced them in 1955. Introduced in May 1987 to supplement route 29, route 28 became the primary Blue Hill Avenue service by December 1989, while route 29 was reduced to rush-hour-only service terminating at Jackson Square. Bus shelters were installed at select stops in 2001. From December 2006 through June 2010, a morning peak short-turn service operated as route 25 between Franklin Park and Dudley (later Ruggles).

The 2003 Program for Mass Transportation evaluated various expansions of the Silver Line, including a brief revival in 2006 of a bus rapid transit (BRT) overlay for route 28 under Silver Line Phase III plans. In 2009, a state proposal introduced the 28X, a limited-stop BRT service along this corridor—the busiest bus corridor in New England—featuring dedicated lanes and queue jump lanes. The project was estimated at $114 million with construction slated to begin in April 2010 aiming for a launch in 2012.

Community opposition emerged due to insufficient local engagement, concerns over parking removal and median strip elimination, as well as anticipated traffic disruptions. Consequently, the state withdrew the proposal late in 2009. In June 2010, MBTA upgraded route 28 vehicles to articulated 60-foot buses to boost capacity; however, some stops in Grove Hall were eliminated to accommodate these larger vehicles, prompting resident objections. A transit needs assessment conducted in 2012 recommended implementing the express service concept of the proposed 28X without new infrastructure investments.

In August 2020, MBTA and Boston jointly applied for $15 million in federal funding toward a $30 million Blue Hill Avenue project that would include center-running bus lanes, targeting completion by the end of 2021; however, funding was denied in September. A subsequent $25 million federal grant application was submitted in July 2021. From August 2021 through February 2022, a city-sponsored pilot provided fare-free rides and all-door boarding on route 28 to reduce delays on this heavily congested corridor. Following this pilot, fare-free service was extended on routes 23, 28, and 29 from March 2022 through February 2026. Additionally, in November 2021 Boston secured a $15 million federal grant supporting Blue Hill Avenue reconstruction efforts.

The May and November 2022 network plans suggested extending route 28 from Roxbury Crossing to via Longwood Medical Area while discontinuing service between Roxbury Crossing and Ruggles. In February 2024, Boston announced a $44 million Blue Hill Avenue reconstruction project including center bus lanes with construction anticipated to commence in 2026.

32

The 32 Wolcott or Cleary Square–Forest Hills Station line operates along Hyde Park Avenue, connecting Forest Hills to Readville and serving the neighborhoods of Jamaica Plain, Roslindale, and Hyde Park. Throughout its entire path, it runs adjacent to the commuter rail tracks.

Prior to 1953, Route 32 functioned as a full trolley service between Forest Hills and Cleary Square before transitioning to trackless trolley operation. By 1958, diesel buses replaced trackless trolleys south of Forest Hills. The trackless trolley turnaround loop was situated at the intersection of Hyde Park Avenue and Pine Street.

In 1981, the former Route 31, which ran from Mattapan Square to Wolcott Square, was combined with Route 32 at Cleary Square, creating the Route 32 Forest Hills–Wolcott Square. Meanwhile, Route 50, serving Cleary Square and Forest Hills via Roslindale, was rerouted to cover the Summer Street Elderly Housing Area. The May and November 2022 network proposals did not suggest any modifications for this route.

39

The 39 Forest Hills Station–Back Bay Station route was introduced in December 1985 to replace Green Line E branch service between Heath Street and Arborway. It parallels the Green Line from Heath Street to Copley and offers connections to the Orange Line and commuter rail at both termini, with Amtrak access available at Back Bay.

Route 39 was notable for being the MBTA’s first line to regularly deploy articulated buses, a practice later adopted by other routes such as the 28 in late 2005. By 2013, it ranked as Boston’s second busiest bus route. Its substantial ridership played a role in the expansion of Forest Hills station during the Casey Arborway project.

The draft network plan released in May 2022 proposed extending Route 39 through via and , substituting segments of routes , , and , while eliminating service between Longwood Avenue and Back Bay. However, the November 2022 draft plan restored Route 39 to its existing alignment and instead increased frequency on Route 47, extending it to Union Square.

57

Serving Boston, Newton, and Watertown, the 57 Watertown Yard–Kenmore Station route replaced the discontinued Green Line A branch in 1969. Historically, Route 57 operated limited-stop service within Boston by not picking up passengers on Commonwealth Avenue between Packard's Corner and Kenmore, but this practice ceased in December 2006. No adjustments were proposed for this route in either the May or November 2022 network plans.

66

The 66 Harvard Square–Nubian Station via Allston route—once a trolley line—originates at Nubian Square in Roxbury and crosses the Southwest Corridor Park near Roxbury Crossing. It briefly shares alignment with Route 39 and the Green Line E branch from Brigham Circle up to Boston’s city limits. Traveling along Harvard Street, it serves Brookline and Allston neighborhoods before diverting through Union Square, then continues along Cambridge Street and North Harvard Street to conclude at Harvard Square in Cambridge.

Route 66 links several major transit nodes including Nubian station (Silver Line), Roxbury Crossing (Orange Line), as well as multiple Green Line stops: Fenwood Rd, Mission Park, Riverway (E branch); Brookline Village (D branch); Coolidge Corner (C branch); Harvard Ave (B branch); along with Harvard on the Red Line. The May and November 2022 network proposals did not include any changes for this route. In August 2024, northbound buses were redirected through the Harvard Bus Tunnel.

71

The 71 Watertown Square–Harvard station route originates from the lower level of the Harvard bus tunnel, proceeds south onto Mount Auburn Street, then travels westward into Watertown, concluding at Watertown Square.

At Harvard, buses reverse direction by exiting the tunnel and looping through Massachusetts Avenue, Garden Street, and Waterhouse Street before heading back. In Watertown, a dedicated right-of-way loop facilitates both turnaround operations and passenger boarding.

Streetcar operations ceased on September 4, 1958, replaced by trackless trolley service which lasted until March 13, 2022. In 2017, routes 71 and 73 participated in a bus rapid transit pilot initiative.

Routes 71 and 73, along with other routes including , were among the final MBTA lines to utilize trolleybuses (commonly called "trackless trolleys") prior to their transition to diesel buses in March 2022. The 2022 network proposals did not suggest any alterations to these routes. Nevertheless, Watertown plans a minor extension toward Watertown Yard as part of redevelopment efforts in Watertown Square.

73

The 73 Waverley Square–Harvard Station starts within the Harvard bus tunnel and shares Mount Auburn Street with route 71 through Cambridge and Watertown. It then follows Belmont Street along the boundary between Belmont and Watertown before continuing on Trapelo Road in Belmont to terminate at Waverley Square. The route completes its loop at the Waverley commuter rail station on the Fitchburg Line.

Originally operated by streetcars until the mid-20th century, route 73 switched to trackless trolley service in 1958, which lasted until March 13, 2022. There were no proposed modifications for this route in the 2022 network redesign plans.

77

The 77 Arlington Heights–Harvard Station line connects Arlington with Harvard station via Massachusetts Avenue. Prior to the Red Line Northwest Extension during the 1980s, routes 77 and 77A served as the main transit options northwest of Harvard, with peak hour frequencies under one minute in 1945. Route 77 converted to diesel buses in 1955; meanwhile, route 77A became a trolleybus line in 1958 to free streetcars for conversion on the Green Line D branch and to eliminate boarding islands for automobile traffic flow. Route 77A managed local stops south of the carhouse while route 77 operated limited-stop service; however, from 1998 through 2005, route 77 gradually absorbed route 77A’s service area. Route 77A was fully discontinued in 2022. In 2017, Arlington pursued private funding to introduce signal priority measures, queue jumps, and potential bus lanes along its segment. The May and November 2022 network plans did not propose any changes for this route.

111

The 111 Woodlawn–Haymarket Station line links downtown Boston with Chelsea via crossings over the Bill Russell and Tobin Bridges. Initially run as streetcars between Chelsea Square and Woodlawn under Boston Elevated Railway management since 1936, it transitioned to bus operation later that same year. The route extended service to Haymarket in April 1975 following the Charlestown Elevated closure; partial extensions beyond Woodlawn occurred starting January 2001. Service beyond Woodlawn ended in September 2019, with short-turn trips at Cary Square replaced by Woodlawn trips as of December 2021. The route ranks among the MBTA’s highest frequency numbered bus lines, operating every five minutes during peak periods. No adjustments were included in the May or November 2022 network proposals.

116/117

The 116 Wonderland Station–Maverick Station via Revere Street and 117 Wonderland Station–Maverick Station via Beach Street routes serviced the areas of East Boston, Chelsea, and Revere. These two lines followed largely overlapping paths through East Boston and Revere, with their only divergence occurring near Wonderland. According to the network plans released in May and November 2022, route 117 was slated for elimination, with the portion between Broadway and Wonderland incorporated into route 116 to enhance bus frequency on this corridor. This adjustment was implemented on December 15, 2024.

See also

• List of MBTA bus routes
• MBTA crosstown bus routes
• MBTA Silver Line (previously included in key routes)
• Free public transport in Boston

External links

• MBTA – routes , , , , , , , , , , , , , ,
• MBTA - Key Bus Route Improvement Program