Boston-area streetcar lines
As with many large cities, a large number of Boston-area streetcar lines once existed. However, only a few remain, namely the four branches of the Green Line and the Ashmont-Mattapan High Speed Line, with only one (the Green Line "E" Branch) running regular service on an undivided street.
The Massachusetts Bay Transportation Authority (MBTA) was formed on August 3, 1964, taking over operations from the Metropolitan Transit Authority (MTA). The MTA itself was formed in 1947 to take over operations of the private Boston Elevated Railway (BERy), which ran rapid transit, streetcars, and buses in the Boston area.
In 1936, the BERy assigned numbers to its routes for map use, but route numbers were not used on buses until the late 1960s (when the colors were assigned to the remaining rail lines). Additionally, the numbers were only kept the same on and after the 1942 revision of the map; before that they were changed with each new version. A few routes were renumbered around 1967, but most routes have kept their original numbers. Routes were numbered roughly clockwise from South Boston to East Boston.
