Key bus routes of the Massachusetts Bay Transportation Authority (MBTA) system were the 15 routes that had high ridership and higher frequency standards than other bus lines, according to the 2004 MBTA Service Policy. Together, they accounted for roughly 40% of the MBTA's total bus ridership. These key bus routes ensured basic geographic coverage with frequent service in the densest areas of Boston, and connected to other MBTA services to give access to other areas throughout the region.
In recognition of their function as part of the backbone MBTA service, the key bus routes were added to newer basic route maps installed in subway stations and other public locations. These schematic route maps show the rail rapid transit routes, bus rapid transit routes, commuter rail services, and key bus routes. The key routes had been treated as a distinct category for the purpose of service improvement, such as trial runs of late-night service, and due to the high volume of passenger traffic they carry, both individual routes and the category as a whole have been the subjects of urban planning and transportation engineering studies. As part of the implementation of the MBTA's Bus Network Redesign program in 2024, the key bus route terminology is being phased out and replaced by a general high-frequency route network.
History
In November 2006, the MBTA launched a concerted effort to improve service quality on key bus routes. The 2008 Service Plan recommended improvements for various lines, including upgrading the 31 bus to key route standards. A second round of upgrades, entitled the Key Routes Improvement Project and costing $10 million in all, was supported by the American Recovery and Reinvestment Act of 2009. The Silver Line services were originally considered part of this program, but were later split off into a separate enhancement project.
The initial Key Routes Improvement Project was concluded in 2013, with some planned upgrades not being made. Due to these changes, the reliability of service (as measured by adherence to posted service frequencies) has been found to be greater on the Key Routes than on others, with 75% versus 61% respectively in June 2017.
A 2012 statistical analysis found that proximity to key bus routes was inversely correlated to taxicab trip generation, whereas taxicab trip generation actually increased with proximity to bus routes overall, suggesting that only the routes with highest frequency were able to compete with taxi service among customers with the option to choose.
In April 2014, extended late-night service on the key bus routes and rapid transit routes was announced, to be operated on a one-year trial basis with service continuation depending on late-night ridership and on corporate sponsorship. , late-night service was cut back from 2:30am to 2:00am, and extended hours were dropped from 5 of the 15 key bus routes. Late-night service was discontinued altogether in March 2016.
The category of key bus routes figured into Boston mayor Marty Walsh's "Go Boston 2030" initiative, which included the goal of having "every Boston household" within a 10-minute walk from a T station or a bus stop on a key route. In addition, a new key route was proposed to connect the Longwood Medical and Academic Area with JFK/UMass station via Roxbury.
In May 2022, the MBTA released a draft plan for a bus network redesign, which included potential changes to most of the key routes. A number of other routes would be upgraded to key bus route frequency, forming a high-frequency bus network complementing the rapid transit network. A revised plan was released in November 2022.
Key routes criteria The MBTA's Service Delivery Policy uses five criteria when determining if a route is part of the Key Bus Routes program. High ridership demand Connectivity within the system Geographic coverage Accommodation of major new development Operation as bus rapid transit
Policy standards A bus route that has been identified as a key route must adhere to two policy standards: Span of service and frequency of service, both of which mandate service levels well above a standard local route. The following tables outline these standards as compared to standard local routes.
Type of RouteSpan of service (minimum)Local Weekday 7:00 AM – 6:30 PM Saturday 8:00 AM – 6:30 PM Sunday 10:00 AM – 6:30 PM Key Weekday 6:00 AM – Midnight Saturday 6:00 AM – Midnight Sunday 7:00 AM – Midnight
Type of RouteFrequency of service (minimum)Local AM & PM peak Every 30 mins All other times Every 60 mins Saturdays & Sundays Every 60 mins Key AM & PM peak Every 10 mins Middays Every 15 mins Evenings, Saturdays & Sundays Every 20 mins
Route list There were 15 key routes within the MBTA system: 1, 15, 22, 23, 28, 32, 39, 57, 66, 71, 73, 77, 111, 116, and 117. Elected officials and members of the public have asked the MBTA for limited-stop or express service along all of these routes.
1
The 1 Harvard Square–Nubian Station, which connects Cambridge with Roxbury, was formed in September 1962 when two routes, split at Massachusetts Avenue (now Hynes Convention Center), were merged – the 76 Harvard–Massachusetts station and the 47 Massachusetts station–Dudley. In May 1987, the route was realigned from its former alignment on Washington Street southeast several blocks onto Albany Street and Melnea Cass Boulevard to serve Boston Medical Center. The route now runs mostly along Massachusetts Avenue, from Harvard, past the Massachusetts Institute of Technology, over the Charles River via the Harvard Bridge into Boston, past the Berklee College of Music to Boston Medical Center, then southwest to Nubian station via Albany Street and Melnea Cass Boulevard.
No changes to the route were proposed in the May and November 2022 network plan. The transit advocacy group Transitmatters rated the 1 bus the slowest and most bunched MBTA bus route, with a mean speed of 6.55 mph and a bunching rate of 17.7% (meaning 1 out of every 6 buses is bunched) during October 2023. Service changes effective August 24, 2025, increased Route 1 frequency to every 15 minutes or less during all operating hours. Service also began operating about one hour longer on Friday and Saturday evenings.
15
The 15 Fields Corner Station–Ruggles Station route runs from Fields Corner station north on Geneva Avenue and Bowdoin Street, west on Hancock Street, and north on Columbia Street to Uphams Corner. It continues west on Dudley Street to Nubian station, then west on Malcolm X Boulevard to and north on Tremont Street to Ruggles station.
Buses started running on the 15 Kane Square–Dudley via Uphams Corner and Dudley Street route on April 6, 1962, replacing trackless trolleys. With the relocation of the Orange Line to the Southwest Corridor in May 1987, the route was extended to Ruggles. Kane Square service was extended slightly to St. Peter's Square on August 25, 2024. All service was extended to Fields Corner on August 24, 2025; previously, only night and weekend service had run past St. Peters Square. Frequency was also increased to every 15 minutes or less during all operating hours.
The May 2022 draft network plan proposed an extension westward to Oak Square (taking over route ), forming an Oak Square–Fields Corner route. The November 2022 draft network plan cut the route back to Ruggles, with route 65 remaining separate.
22
The 22 Ashmont Station–Ruggles Station via Talbot Ave begins at Ashmont and runs on a northwesterly route to the former site of Egleston station. From there it continues north on Columbus Avenue and Tremont Street along the course of the Orange Line before ending at Ruggles.
Buses replaced trackless trolleys on the 22 on April 6, 1962, running as the 22 Ashmont–Dudley via Talbot and Warren. This route, rather than turning off Blue Hill Avenue onto Seaver Street, continued north a bit further and then went north on Warren Street to end at . It was extended to Ruggles in May 1987 along with the relocation of the Orange Line to the Southwest Corridor. The May and November 2022 network plans proposed that the inner terminal be changed to the Longwood Medical Area. Service changes effective August 24, 2025, increased Route 22 frequency to every 15 minutes or less during all operating hours. Service also began operating about one hour longer on Friday and Saturday evenings.
23 The 23 Ashmont Station–Ruggles Station via Washington Street has the same endpoints as the 22, but uses a mostly different route. It starts out of Ashmont on Talbot Avenue, but turns north on Washington Street, following that onto Warren Street to Nubian station. From Nubian, the 23 heads west on Malcolm X Boulevard to Roxbury Crossing and north on Tremont Street to Ruggles station.
Buses replaced trackless trolleys on April 7, 1962, on the 22 Ashmont–Dudley via Washington Street and Warren. It was extended to Ruggles in May 1987 along with the relocation of the Orange Line to the Southwest Corridor.
A 2017 study of fare-card and vehicle-location data suggested that the 23 and 28 routes were overcrowded, and that this could be ameliorated by extending the 29 route and increasing its service frequency. A city-funded program includes fare-free service on routes 23, 28, and 29 from March 1, 2022, to February 28, 2026. No changes to the route were proposed in the May and November 2022 network plans. Service changes effective August 24, 2025, increased Route 23 frequency to every 15 minutes or less during all operating hours. Service also began operating about one hour later in the evening.
28
The 28 Mattapan Station–Ruggles Station route provides service through the Grove Hall and Mattapan neighborhoods on Blue Hill Avenue, a major radial arterial. Blue Hill Avenue has long been a busy trunk route; in 1945, route 29 Mattapan–Egleston peaked at 1.5 minute headways during the morning rush hour. Streetcars formerly had a dedicated right-of-way on Blue Hill Avenue; streetcars were moved into mixed traffic in stages between 1940 and 1950, and replaced with buses in 1955.
With the May 1987 changes to the bus network, route 28 was established to supplement route 29 service; both ran from Mattapan to Ruggles via different routings. In December 1989, route 28 became the dominant service on Blue Hill Avenue, and route 29 was relegated to a rush-hour-only route running only to Jackson Square. Shelters were added at some stops in 2001. From December 2006 to June 2010, short turn service between Franklin Park and Dudley (Ruggles after March 2007) was operated in the morning peak as route 25.
A number of Silver Line expansion corridors were considered in the 2003 Program for Mass Transportation (PMT); most were given brief consideration but not acted upon. One, a bus rapid transit (BRT) express overlay for the 28, was briefly revived in 2006 as part of Silver Line Phase III plans. In 2009, the state proposed to add a limited-stop BRT line called the 28X on the corridor, which was then the busiest bus corridor in New England. The plan called for dedicated bus lanes on Blue Hill Avenue and queue jumps on Warren Avenue. The project was expected to cost $114 million. Construction was to begin in April 2010, with initial service at the beginning of 2012.