thumb|right|upright=1.2|Geographic map of MBTA crosstown bus routes as originally introduced. The CT1 is colored aqua, the CT2 navy, and the CT3 peach.
The Massachusetts Bay Transportation Authority (MBTA) began operating three specially designated crosstown bus route in the Boston metropolitan area in 1994. Intended as a limited-stop bus connecting major points, the weekday-only routes largely paralleled MBTA bus local routes, but with fewer stops to reduce travel times. Only one of the three routes – route CT3 – still operates.
The three crosstown routes – CT1, CT2, and CT3 – began operation in 1994. Eight additional routes numbered CT4 through CT11 were proposed in 2001 as part of an interim phase of the Urban Ring Project to provide circumferential service bypassing the crowded downtown subway stations, but were never put in service. Route CT1 was merged with route in 2019. Route CT2 was merged with route 85 in 2026. Route CT3 is planned to be replaced by a new route 12 in the late 2020s.
System development
The need for better circumferential transit in Boston was raised by the 1972 Boston Transportation Planning Review. The 1989 Circumferential Transit Feasibility Study began planning for the Urban Ring Project, which was to be a high-capacity circumferential line connecting hubs including Logan Airport, Kendall Square, and the Longwood Medical Area (LMA) outside downtown Boston. The MBTA announced plans for a three-route pilot program in May 1994. It was to include two previously proposed routes plus a Central Square–Boston Medical Center route, all operating with limited stops.
The three crosstown routes began operation on September 26, 1994. The Central–Boston Medical Center route was designated CT1, the Kendall–Ruggles route CT2, and the LMA–Andrew route CT3. In January 1995, governor Bill Weld vetoed several sections of a transportation bond bill, including a truck ban on MDC parkways. The ban would have also applied to buses, affecting the crosstown bus routes.
Eight additional routes numbered CT4 through CT11 were proposed in 2001 as part of an interim phase of the Urban Ring Project to provide circumferential service bypassing the crowded downtown subway stations, but were never put in service.
CT1
Route CT1 (internally coded 701) ran between Central Square in Cambridge and Boston Medical Center, mostly along Massachusetts Avenue. The majority of its route was a limited-stop version of route 1. Route CT1 was merged into route 1 in September 2019 to provide more frequent service and more consistent headways.
Stop listing
{| class="wikitable"
!Stop
!Major connections
| garage=Albany Garage and Cabot Garage
| open=September 26, 1994
| close=April 5, 2026
| timetable_link =
<!--thumb|A Route CT2 bus with crosstown bus branding at in 2007-->
Route CT2 (internally coded 747) ran between Sullivan Square station in Charlestown and Ruggles station in Roxbury via Kendall Square in Cambridge. The southern part of the route roughly paralleled route . In May 2022, the MBTA released a draft plan for a systemwide network redesign, which called for route CT2 to be discontinued. Portions of the route would be covered by extensions of routes and with higher frequency. A revised proposal in November 2022 called for route CT2 to be replaced by route . It would follow the existing CT2 routing between Ruggles and Union Square, then continue to Assembly Square via Cross Street and Broadway. Route CT2 was replaced with route 85 on April 5, 2026. Unlike the 2022 proposal, the new 85 follows the existing CT2 routing between Union Square and Sullivan Square, and terminates on Grand Union Boulevard rather than at Assembly station. It also makes all stops rather than the limited stops of the CT2.
Stop listing
{| class="wikitable"
!Stop
| garage=Albany Garage and Cabot Garage
| open=September 26, 1994
| close=
| timetable_link = CT3
Route CT3 (internally coded 708) operates between Longwood Medical Area (LMA) and Andrew station entirely within the city of Boston, roughly paralleling route . From Andrew station, it runs west on Southampton Street (some trips via Newmarket Square) and northeast on Albany Street to Boston Medical Center, then southwest on Harrison Avenue and west on Melnea Cass Boulevard to Ruggles station. It continues west on Ruggles Street and Fenway, then makes a one-way clockwise loop through the LMA on Avenue Louis Pasteur, Longwood Avenue, Brookline Avenue, and Fenway. As of , the route has 22-minute headways at peak hours and 70-minute headways midday; it does not have evening or weekend service. The route operates with standard transit buses based at Albany Garage and Cabot Garage in Boston.
The CT3 route originally operated between Andrew and the LMA; it was extended to Logan Airport in December 1998. The extension (internally coded 709) was dropped due to low ridership in March 2002. Two early morning trips were kept as route 171, running from to Logan. They are through-routed with route 15 trips.