553 (MBTA bus)

The Massachusetts Bay Transportation Authority bus division operates bus routes in the Boston, Massachusetts metropolitan area. All routes connect to MBTA subway, MBTA Commuter Rail, and/or other MBTA Bus services. Many routes are descendants of the streetcar routes of the Boston Elevated Railway, or of suburban companies including the Eastern Massachusetts Street Railway, Middlesex and Boston Street Railway, and Newton and Boston Street Railway.

The Silver Line is a bus rapid transit system marketed as rapid transit. It is divided into two branches: Waterfront service (SL1, SL2, and the rush-hour Shuttle) that runs through the South Boston Transitway tunnel, and Washington Street service (SL4 and SL5) that runs on the surface via Washington Street. The Waterfront service costs the same as a subway fare, while the Washington Street service costs a regular bus fare.

The SL5 route was created in 2002 as a replacement for the Washington Street Elevated. The Shuttle route began operations in 2004, followed by the Sl1 and SL2 in 2005 when dual-mode buses became available. The SL4 was introduced in 2009 as a replacement for the canceled Phase III tunnel.

The crosstown (CT) buses provide limited-stop service on three routes that connect major subway and bus transfer points. The routes were created by the MBTA in 1994.

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