15 (MBTA bus)

Massachusetts Bay Transportation Authority (MBTA)

Company type	Public agency
Industry	Public transportation
Founded	August 1, 1964 (1964-08-01)
Headquarters	Boston , United States
Area served	Greater Boston, Massachusetts
Products	Bus, subway, commuter rail, ferry services
Owner	Commonwealth of Massachusetts
Website	mbta.com

Primary bus routes within the Massachusetts Bay Transportation Authority (MBTA) network referred to the 15 lines with the greatest ridership and service frequency benchmarks as defined by the 2004 MBTA Service Policy. Collectively, these routes represented approximately 40% of the MBTA's overall bus passenger trips. They offered frequent transit options in Boston’s most densely populated neighborhoods and linked seamlessly with other MBTA modes, facilitating extensive regional connectivity.

Designated as a core component of the MBTA system, these primary bus routes were highlighted on updated transit maps displayed in subway stations and public areas alongside rapid transit and commuter rail lines. Due to their substantial passenger volumes, they were prioritized for enhancements such as late-night service pilots and have been central to various urban planning and transportation engineering analyses. The 2024 Bus Network Redesign initiative is phasing out the key route classification in favor of a more expansive high-frequency network.

History

In November 2006, the MBTA initiated a program aimed at improving its primary bus routes. The 2008 Service Plan recommended service enhancements for multiple lines, including promoting Route 31 to key route status. Subsequently, a $10 million Key Routes Improvement Project was launched with funding from the American Recovery and Reinvestment Act of 2009. This project initially encompassed Silver Line services, which were later managed independently. Although not all planned upgrades were completed by the project’s conclusion in 2013, reliability on these primary routes has consistently exceeded that of other lines, with on-time performance recorded at 75% compared to 61% as of June 2017.

A study conducted in 2012 demonstrated that areas near key bus routes experienced decreased demand for taxi trips, suggesting these high-frequency routes effectively attract riders who might otherwise choose taxis.

Starting in April 2014, extended late-night operations on key bus and rapid transit lines were launched as a one-year pilot contingent on ridership levels and sponsorship support. By April 2015, late-night service hours were curtailed and eliminated from five key routes; ultimately, all late-night operations ceased in March 2016.

Key bus routes played a significant role in Boston Mayor Marty Walsh’s "Go Boston 2030" plan, which aimed to ensure every household was within a ten-minute walk of either a T station or a key bus stop. One proposed new key route was designed to connect the Longwood Medical Area with JFK/UMass station via Roxbury.

In May 2022, the MBTA unveiled a draft Bus Network Redesign proposal recommending modifications to most key routes while elevating several others into a high-frequency network intended to complement rapid transit services. An updated plan was released in November 2022.

Criteria for Key Routes

According to the MBTA’s Service Delivery Policy, Key Bus Routes are selected based on five factors:

• Elevated ridership levels
• Integration within the transit system
• Geographic service coverage
• Support for significant new developments
• Functioning as bus rapid transit

Service Standards

Key bus routes are subject to more rigorous requirements regarding service hours and frequency compared to standard local routes. The minimum operational spans are:

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

The minimum frequency requirements are:

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

Route Overview

The MBTA identified 15 principal routes: 1, 15, 22, 23, 28, 32, 39, 57, 66, 71, 73, 77, 111, 116, and 117. These corridors have been prioritized due to frequent public and official appeals for limited-stop or express service enhancements aimed at boosting transit performance and addressing substantial ridership.

1

The 1 Harvard Square–Nubian Station line connects Cambridge with Roxbury. It originated in September 1962 by combining two previously separate routes that met at Massachusetts Avenue (currently Hynes Convention Center): the 76 Harvard–Massachusetts station and the former 47 Massachusetts station–Dudley. In May 1987, this route was adjusted from Washington Street southeastward along Albany Street and Melnea Cass Boulevard to provide service to Boston Medical Center. Its main corridor follows Massachusetts Avenue, beginning at Harvard, passing the Massachusetts Institute of Technology, crossing the Charles River via the Harvard Bridge, continuing past the Berklee College of Music to Boston Medical Center, then heading southwest to Nubian station through Albany Street and Melnea Cass Boulevard.

By 2015, Cambridge intended to introduce signal priority at certain intersections for route 1 to enhance operational efficiency. The network plans released in May and November 2022 did not include any modifications to this route.

Transit advocacy organization Transitmatters identified the number 1 bus as the MBTA’s slowest and most prone to bunching, recording an average velocity of only 6.55 mph and a bunching incidence of 17.7% in October 2023.

15

The 15 Fields Corner Station or St. Peter's Square–Ruggles Station route operates from St. Peter's Square in northern Dorchester, proceeding north on Bowdoin Street, then west along Hancock Street, followed by a northbound segment on Columbia Street reaching Uphams Corner. Continuing westward on Dudley Street to Nubian station, it then travels west via Malcolm X Boulevard before turning north on Tremont Street toward Ruggles station. During nights and weekends, service ends at Fields Corner station, with buses navigating Geneva Avenue and Bowdoin Street back to St. Peter's Square.

Bus service on the route initially named Kane Square–Dudley via Uphams Corner commenced on April 6, 1962, replacing former trackless trolley operations. Following the Orange Line’s relocation to the Southwest Corridor in May 1987, the route was extended to reach Ruggles. On August 25, 2024, service was slightly extended from Kane Square to St. Peter’s Square.

The draft network plan published in May 2022 proposed a westward extension of this route to Oak Square, effectively replacing route , thus creating an Oak Square–Fields Corner corridor. Nonetheless, the November 2022 draft plan reversed this change by truncating the route back to Ruggles and leaving route 65 intact.

22

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

On April 6, 1962, buses replaced the trackless trolleys operating this line, initially designated as the 22 Ashmont–Dudley via Talbot and Warren. Unlike the current path, the route formerly extended northward on Warren Street to . In May 1987, coinciding with the Orange Line relocation, the service was lengthened to reach Ruggles. The network drafts from May and November 2022 suggested modifying the inner terminal to Longwood Medical Area.

23

The 23 Ashmont Station–Ruggles Station via Washington Street shares its start and end points with route 22 but follows a distinct course. Departing from Ashmont on Talbot Avenue, it heads north on Washington Street, then continues along Warren Street to Nubian station. From there, it travels west on Malcolm X Boulevard to Roxbury Crossing, and finally moves north on Tremont Street until reaching Ruggles station.

This route transitioned from trackless trolleys to buses on April 7, 1962, initially operating as the 22 Ashmont–Dudley via Washington Street and Warren. The extension to Ruggles was implemented in May 1987 alongside the Orange Line's realignment.

A study conducted in 2017 identified overcrowding issues on routes 23 and 28 that could be alleviated by lengthening route 29 and increasing its service frequency. Additionally, a city-funded fare-free initiative covers routes 23, 28, and 29 from March 1, 2022, through February 28, 2026. No modifications were proposed for route 23 in either the May or November 2022 network plans.

28

The 28 Mattapan Station–Ruggles Station line connects the Grove Hall and Mattapan neighborhoods via Blue Hill Avenue, a major thoroughfare. Historically, transit activity peaked here with streetcars operating at intervals as short as 1.5 minutes on route 29 in 1945. Buses replaced streetcars in 1955. Established in 1987 to complement route 29, route 28 became the primary service along Blue Hill Avenue by 1989. Passenger shelters were installed in 2001, and peak short-turn trips operated as route 25 between 2006 and 2010.

The 2003 Program for Mass Transportation explored several Silver Line expansions, including a Bus Rapid Transit (BRT) overlay for route 28, which was briefly reconsidered during Silver Line Phase III planning. In 2009, a limited-stop BRT service named 28X was proposed for what is considered New England’s busiest bus corridor. This plan included dedicated bus lanes and queue jump lanes, with an estimated cost of $114 million and construction slated for 2010–2012.

Nevertheless, local opposition arose due to inadequate community engagement, concerns over parking loss, and potential long-term construction disruptions. As a result, the state withdrew the proposal by late 2009. In June 2010, MBTA introduced articulated 60-foot buses on route 28 to boost capacity despite community concerns over stop eliminations in Grove Hall. The Roxbury–Dorchester–Mattapan Transit Needs Study of 2012 recommended implementing the express-style service of the proposed 28X without requiring new infrastructure.

In August 2020, MBTA and Boston jointly applied for $15 million in federal funding toward a $30 million Blue Hill Avenue project featuring center-running bus lanes aimed for completion by late 2021; however, this application was denied in September. A subsequent $25 million federal grant request was submitted in July 2021. Between August 2021 and February 2022, a city-sponsored pilot program costing $500,000 offered fare-free rides and all-door boarding on route 28 to improve travel times. Following this pilot’s success, fare-free service for routes 23, 28, and 29 was extended through February 2026. In November 2021, Boston secured a $15 million federal grant toward the $39.5 million Blue Hill Avenue reconstruction project.

The network proposals released in May and November of 2022 recommended extending route 28 beyond Roxbury Crossing to via Longwood Medical Area while eliminating service between Roxbury Crossing and Ruggles. In February 2024, Boston announced plans for a $44 million Blue Hill Avenue reconstruction that includes center-running bus lanes with construction anticipated to commence in 2026.

32

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

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

In 1981, Route 31, which ran between Mattapan Square and Wolcott Square, was combined with Route 32 at Cleary Square, resulting in the creation of Route 32 Forest Hills–Wolcott Square. Meanwhile, Route 50, which served both Cleary Square and Forest Hills via Roslindale, was redirected to cover the Summer Street Elderly Housing area. The network plans released in May and November 2022 did not recommend any modifications to this route.

39

The 39 Forest Hills Station–Back Bay Station route was introduced in December 1985 as a replacement for the Green Line E branch service from Heath Street to Arborway. It runs parallel to the Green Line from Heath Street to Copley and provides connections to both the Orange Line and commuter rail at each terminus, with Amtrak access available at Back Bay.

Route 39 was pioneering in its regular use of articulated buses within the MBTA system, a feature later adopted by other routes such as the 28 in late 2005. By 2013, it ranked as Boston’s second busiest bus line. Its substantial ridership played a key role in prompting the expansion of Forest Hills station during the Casey Arborway redevelopment.

The draft network plan from May 2022 proposed extending Route 39 through several new areas including , , and , substituting portions of routes , , and , while eliminating service between Longwood Avenue and Back Bay. However, the November 2022 plan restored Route 39 to its prior routing and instead extended a more frequent Route 47 to Union Square in Somerville.

57

Serving Boston, Newton, and Watertown, the 57 Watertown Yard–Kenmore Station route took over after the discontinuation of the Green Line A branch in 1969. Historically, Route 57 provided limited-stop service within Boston—specifically no passenger pickups on Commonwealth Avenue between Packard's Corner and Kenmore—but this practice ceased in December 2006. The May and November 2022 network proposals did not include any changes for this route.

66

The 66 Harvard Square–Nubian Station via Allston line, once operated as a trolley, originates at Nubian Square in Roxbury and crosses the Southwest Corridor Park near Roxbury Crossing. It briefly overlaps with Route 39 and the Green Line E branch from Brigham Circle up to Boston’s city boundary. Following Harvard Street, it serves Brookline and Allston neighborhoods before diverting through Union Square (Allston), then continuing along Cambridge Street and North Harvard Street to conclude at Harvard Square in Cambridge.

This route offers connections to multiple transit lines: Silver Line at Nubian station; Orange Line at Roxbury Crossing; Green Line E branch stops including Fenwood Road, Mission Park, and Riverway; Green Line D branch at Brookline Village; Green Line C branch at Coolidge Corner; Green Line B branch at Harvard Avenue; and Red Line at Harvard station. No amendments were recommended for this route in either the May or November 2022 network plans. In August 2024, northbound buses were rerouted through the Harvard Bus Tunnel.

71

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

At Harvard, buses complete their turnaround by exiting the tunnel, making a left onto Massachusetts Avenue, then turning right onto Garden Street, followed by another right onto Waterhouse Street, before returning to Massachusetts Avenue to re-enter the tunnel. In Watertown, a privately owned right-of-way loop allows buses to turn around and facilitate passenger boarding.

Streetcar operations ceased on September 4, 1958, succeeded by trackless trolley service until March 13, 2022. In 2017, the 71 and 73 routes were chosen for a pilot bus rapid transit initiative.

Routes 71 and 73, together with other select routes, maintained trackless trolley service long after the majority of MBTA trolleybus lines were discontinued, representing the last vestiges of Boston’s once extensive trolleybus network. These routes transitioned to diesel buses in March 2022. While no modifications were proposed in the 2022 network redesign plans, Watertown is considering a minor extension to Watertown Yard as part of a redevelopment project in Watertown Square.

73

The 73 Waverley Square–Harvard Station route also begins within the Harvard bus tunnel and travels alongside the 71 along Mount Auburn Street through Cambridge and Watertown. It then diverges onto Belmont Street, which borders both Belmont and Watertown, continuing along Trapelo Road in Belmont before terminating at Waverley Square. The route loops at the Waverley commuter rail station on the Fitchburg Line.

Originally operated by streetcars until the 1950s, trackless trolley service began providing short-turn trips from Harvard to Benton Square in 1957; the entire route converted to trackless trolleys in 1958. This mode remained in use until March 2022. Recent network plans have not suggested any alterations to Route 73.

77

The 77 Arlington Heights–Harvard Station line links Arlington with Harvard station via Massachusetts Avenue. Prior to the Northwest Extension of the Red Line in the 1980s, routes 77 and 77A offered primary transit service northwest of Harvard, with combined streetcar frequencies under one minute during peak hours in 1945. Route 77 switched to diesel buses in 1955; meanwhile, route 77A (a Harvard–North Cambridge carhouse short-turn) became a trolleybus route in 1958 to free streetcars for conversion of the Highland branch and to eliminate boarding islands that impeded automobile traffic. Route 77A managed all local stops south of the carhouse while route 77 operated as limited-stop service. Between 1998 and 2005, route 77 largely took over service from route 77A, which was fully discontinued in 2022. In 2017, Arlington pursued private funding aimed at implementing signal priority measures, queue jumps, and potential bus lanes along its segment. No route modifications appeared in either the May or November 2022 network proposals.

111

The 111 Woodlawn–Haymarket Station route serves downtown Boston and portions of Chelsea via crossings over the Bill Russell and Tobin Bridges. Initially operated as streetcars between Chelsea Square and Woodlawn, buses replaced streetcars in October 1936. The route extended to Haymarket following the closure of the Charlestown Elevated in April 1975; partial extensions beyond Woodlawn occurred in January 2001. Service beyond Woodlawn ended in September 2019; Cary Square short-turn trips were supplanted by full Woodlawn trips as of December 2021. The 111 is among the MBTA's most frequent numbered bus lines, operating at five-minute intervals during peak periods. No changes were recommended in either the May or November 2022 network plans.

116/117

The 116 Wonderland Station–Maverick Station via Revere Street and 117 Wonderland Station–Maverick Station via Beach Street routes connected East Boston, Chelsea, and Revere. While both lines largely overlapped their courses through East Boston and Revere, their paths diverged near Wonderland. In the network plans released in May and November 2022, route 117 was slated for elimination, with the portion between Broadway and Wonderland station incorporated into an extended route operating at enhanced bus frequencies. 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