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.

ubway

The subway system consists of four trunk lines, all of which meet downtown. Each is assigned a color, as follows:
*The Red Line used to terminate at Harvard University.
*The Green Line runs to the western suburbs, notably Brookline and Newton. Its color assignment derives from the Emerald Necklace, a string of parks that the line's "D" branch operates through.
*The Orange Line's trains were colored orange when they were run by the Boston Elevated Railway. Also, it runs under part of Washington Street, a piece of which was called Orange Street until 1788.
*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

The "E" branch of the Green Line ran to Forest Hills/Arboretum until 1985, when the line was "temporarily" cut back to Heath Street. As of early 2008, the Green Line has still not been re-extended to Forest Hills.

History

Until 1965, the lines were called by their names:
*The Red Line was the Cambridge-Dorchester Tunnel (the branch to Braintree didn't exist yet; 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-Government Center (Green Line "B")
*69 Watertown-Park Street (Green Line "A")

On August 26, 1965, the current colors were assigned. In 1967 the letters were assigned, ending the use of map numbers for the remaining rail routes. 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". [http://world.nycsubway.org/perl/show?35539] Watertown ("A") cars never used these new rollsigns before permanent bustitution in 1969. "X" is used for out-of-service cars. [http://206.103.49.193/boston/htm/bos391.htm]

On some later rollsigns, short-turn trips were displayed with a slash through the letter. This use included:
*D Government Center [http://206.103.49.193/boston/htm/bos044.htm]
*E Heath Street [http://world.nycsubway.org/perl/show?33110]
*E Brigham Circle [http://206.103.49.193/boston/htm/bos420.htm] 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 letters. [http://groups-beta.google.com/group/misc.transport.urban-transit/messages/0d2cdf18207974f5,900589f582f46d05,1374c25c232cceb5,d85cdcf8689369d2,51ec5512f2f5ddfe,b0e411bbf4100e9a,3dd0d276d23e57db,8544edf31aae63df,0f7d89eb1223fd41,1a0fc52080217d24?hl=en&thread_id=a39e96e4ecc836ca&mode=thread&noheader=1&_done=%2Fgroup%2Fmisc.transport.urban-transit%2Fbrowse_frm%2Fthread%2Fa39e96e4ecc836ca%2Fa9a23545f09a35c6%3F#doc_d85cdcf8689369d2]