MBTA nomenclature

The Massachusetts Bay Transportation Authority (MBTA) maintains a large public transit system in the Boston, Massachusetts area, and uses various methods to name and number their services for the convenience of users.

Subway

The subway system consists of four trunk lines, all of which meet downtown. Each is assigned a color, as follows:
*The Red Line, originally from Cambridge to Dorchester.
*The Green Line runs to the western suburbs, notably Brookline and Newton.
*The Orange Line's trains kept Boston Elevated Railway livery.
*The Blue Line runs under Boston Harbor and to Revere Beach.
The Red Line has two branches, in the south, called by their terminals – Ashmont and Braintree. Additionally, the Ashmont–Mattapan High Speed Line, a streetcar line to Mattapan, is also colored red. Some trains use the letters A, B, and C for Ashmont, Braintree and Alewife (the north terminal) respectively.

The Green Line is a streetcar/ light rail system with four branches to the west, labeled "B" to "E" from north to south. The trains operate underground in the downtown area; outside of downtown, all but the "D" branch run along city streets, with frequent grade crossings at intersections. Rollsigns and newer electronic signs use the following labels:
* B – Boston College via Commonwealth Avenue
* C – Cleveland Circle via Beacon Street
* D – Riverside via Highland branch
* E – Heath Street via Huntington Avenue

Subway history

Until 1965, the lines were called by their names:
*The Red Line was the Cambridge–Dorchester tunnel (the branch to Braintree did not yet exist; it follows an Old Colony Railroad right-of-way). The Ashmont–Mattapan High Speed Line was simply called that.
*The Green Line was five streetcar lines feeding into the Tremont Street subway, named by their western terminals or the streets they ran along.
*The Orange Line was the Main Line Elevated or Forest Hills–Everett Elevated.
*The Blue Line was the East Boston Tunnel and Revere Extension.

They were also known by various numbers, used only on maps (see below for more details), as part of an integrated system of rapid transit, streetcars and buses:
*1 Harvard–Ashmont (Red Line)
*2 Everett–Forest Hills (Orange Line)
*3 Bowdoin–Wonderland (Blue Line)
*4 Riverside-Lechmere (Green Line D)
*28 Mattapan–Ashmont (Red Line)
*39 Arborway–Park Street (Green Line E)
*57 Heath Street–Government Center (Green Line "E" short turns)
*61 Cleveland Circle–North Station (Green Line C)
*62 Boston College–Park Street (Green Line B)
*69 Watertown–Park Street (Green Line A)

After taking over operations in August 1964, the MBTA began rebranding many elements of Boston's public transportation network. On August 26, 1965, the four rapid transit lines were assigned colored names related to their history and geography. The Red Line was named for Harvard University's crimson branding, the Blue Line for passing under Boston Harbor and along Revere Beach, the Green Line for running along the Emerald Necklace, and the Orange Line for running under a section of Washington Street originally known as Orange Street. When designing the rebranding, Cambridge Seven Associates originally planned for yellow instead of orange, but yellow was rejected after testing.

On August 26, 1965, the current colors were assigned. The Green Line branches were lettered A to E in 1967, ending the use of map numbers for the remaining rail routes. The A branch was discontinued in 1969, before lettered rollsigns were ever used on the line. As cars were interchangeable between the Green Line and Ashmont–Mattapan Line, rollsigns also included the letter F for Mattapan service, but this was later changed to M


On some later rollsigns, short-turn trips were displayed with a slash through the letter. This use included:
*D Government Cente

*E Heath Stree

*E Brigham Circl

Many rollsigns only use the letters for outbound trips, with no letters next to downtown destinations. When the letters were first applied, the inbound destinations all used letter