Tremont Street Subway served a light rail station on the MBTA Green Line system, and is located on the southeast corner of Boston Common at the intersection of Boylston Street and Tremont Street called Boylston station.
 The Boylston Street subway runs roughly eastwest through the Back Bay neighborhood, with stations at Arlington, Copley, Hynes Convention Center, and Kenmore; it connects to the Tremont Street subway at Boylston
In 1980, the MBTA began a study of the "Green Line Northwest Corridor" (from Haymarket to Medford) with three area of focus: replacement of the Causeway Street elevated, replacement of Lechmere station, and extension beyond Lechmere

