In 1965, the MBTA assigned colors to its four rapid transit lines and lettered the branches of the Green Line from north to south. However, shortages of streetcars, among other factors, eventually caused bus substitution of rail service on two branches of the Green Line. In 1969, the A branch was replaced by bus service in its entirety. In 1985, the portion of the E branch from Heath Street to Arborway was replaced by buses.
