improved, the BERy began replacing some of its streetcar lines with buses. These conversions accelerated in the 1930s, with some routes also converted to trolleybuses (locally referred to as 'trackless trolleys'). Bus conversions paused during World War II when gasoline and rubber were in limited supply, but resumed in the late 1940s. In 1947 the Metropolitan Transit Authority (MTA) was formed to take over the streetcar, bus, and rapid transit operations of the Boston Elevated Railway. It continued to convert lines from streetcar (and trackless trolley) to bus. In 1964 the MTA's operations were in turn taken over by the Massachusetts Bay Transportation Authority (MBTA), which also took over other bus systems running to suburban towns outside the MTA area. By this point the only remaining streetcar lines were five routes running into the Tremont Street Subway and one route on private right-of-way between Mattapan and Ashmont at the end of the Red Line. These were respectively designated as the Green Line branches A thru E and as part of the Red Line. The Green Line "A" branch was subsequently abandoned in 1969 and the "E" branch south of Heath Street abandoned in 1985. Route numbering 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 even through conversions from streetcar to trackless trolley to bus. Routes were numbered roughly clockwise from South Boston to East Boston. Timeline of streetcar abandonments This is a table of when each streetcar line was converted to trackless trolley or bus. Only information post-1940 is complete. MTA streetcar routes as of 1953 As of early 1953 the Metropolitan Transit Authority operated the following streetcar routes. All lines were connected via trackage to the Tremont Street subway (Green Line), but only the 9, 39, 43, 57, 61, 62 and 69 actually operated in the subway. Eastern Massachusetts Street Railway routes The Eastern Massachusetts Street Railway (EMSR) operated lines between Boston and towns north and south of the Boston area, including Lynn, Salem, Reading, Lowell, Lawrence, Quincy, Hingham, and Brockton. It