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| image = MBTA Green Line B.jpg | image_width = 300px | caption = Green Line train built by AnsaldoBreda on the "B" Branch | type = Light rail | system = Massachusetts Bay Transportation Authority | status = | locale = Boston, Massachusetts | start = East terminals: Lechmere (E) North Station (C) Park Street (B, D) | end = West terminals: Boston College (B) Cleveland Circle (C) Riverside (D) Heath Street (E) | stations = 66 (total) | routes = * "B" Branch (Commonwealth Ave) (Boston College) * "C" Branch (Beacon Street) (Cleveland Circle) * "D" Branch (Highland) (Riverside) * "E" Branch (Huntington Avenue) (Heath Street) | ridership = 229,500 (Q2 2015) | open = (Tremont Street Subway) | close = | owner = MBTA | operator = MBTA | character = Subway, grade-separated ROW, street running | stock = Kinki Sharyo Type 7 AnsaldoBreda Type 8 | linelength = 〔 | tracklength = | notrack = | gauge = | minradius = | el = 600 V DC Overhead catenary | speed = | elevation = | map = }} The Green Line is a light rail system run by the Massachusetts Bay Transportation Authority (MBTA) in the Boston, Massachusetts, metropolitan area. It is the oldest Boston subway line, with tunnel sections dating to 1897. It runs underground through downtown Boston, and on the surface on several radial boulevards and into inner suburbs. With a daily weekday ridership of over 220,000 in late 2014, it is the most heavily-used light rail system in the country. The line was assigned the green color in 1967 during a systemwide rebranding because several branches pass through sections of the Emerald Necklace of Boston. The four branches are the remnants of a large streetcar system, which began in 1856 with the Cambridge Horse Railroad and was consolidated until the Boston Elevated Railway several decades later. The Tremont Street Subway—the oldest subway tunnel in North America—opened its first section on September 1, 1897, to take streetcars off overcrowded downtown streets; it was extended five times over the next five decades. The streetcar system peaked in size around 1930 and was gradually replaced with trackless trolleys and buses, with cuts as late as 1985. A new branch opened on a converted commuter rail line in 1959; the Green Line Extension project will add two new branches into Somerville and Medford in 2017 and 2020. ==Route description== The line has its northern terminus at Lechmere in eastern Cambridge with connections to numerous bus routes serving Cambridge and Somerville. From there it runs south over the Lechmere Viaduct and into an extension of the Tremont Street Subway under downtown Boston to the Boston Common. It continues west in the Boylston Street Subway to Kenmore Square. The Green Line tunnels through Downtown Boston and the Back Bay are collectively referred to as the Central Subway. The "E" Branch serves Lechmere and splits just west of Copley, running southwest through the Huntington Avenue Subway, ramping up to the surface at Northeastern University near Boston's Symphony Hall. It continues along Huntington Avenue, and terminating at Heath Street near V.A. Medical Center. Until 1985, the line continued though Jamaica Plain to Arborway. The "B", "C", and "D" Branches diverge west of Kenmore Square. From south to north, they are as follows: The "D" Branch surfaces onto the grade-separated Highland Branch, a branch of the Boston and Albany Railroad until 1958. It runs about ten and a half miles to Riverside, the primary light rail maintenance facility and major park and ride facility, on the banks of the Charles River and half a mile from the interchange of I-90 (Massachusetts Turnpike) and I-95 (Route 128 Circumferential Highway). The "C" Branch surfaces onto Beacon Street, running to Cleveland Circle at the Chestnut Hill Reservoir. The "B" Branch surfaces onto Commonwealth Avenue. It runs past Boston University, passes within a quarter mile of Cleveland Circle, where a connection to the latter runs down Chestnut Hill Ave., and continues to Boston College. The "A" Branch diverged from Commonwealth Ave. west of Boston University and ran to Watertown, across the Charles River from Watertown Square, until 1969. Although the route-letter scheme had been introduced two years prior to its closure, the "A" designation was never signed on streetcars to Watertown. It was, however, included in the destination signs on the Boeing-Vertol LRVs ordered in the mid-1970s, when reopening Watertown was under consideration. The A line tracks remained in non-revenue service to access maintenance facilities at Watertown until 1994. Not only was there community opposition to restoration, but the tracks would have required a complete rehabilitation. The Lechmere Viaduct originally connected to the Central Subway via the Causeway Street Elevated, a half-mile-long structure running in front of North Station and the Boston Garden sports complex. A new tunnel, running behind North Station and the new TD Garden (which replaced the Boston Garden) and connecting to a new underground Green Line and Orange Line transfer station, was built to replace it. Bus shuttle service ran from Government Center (Scollay Square) to Lechmere from June 2004 until November 12, 2005 during the final stages of construction. The original Tremont Street Subway south of Boylston station has been closed since 1962, when the last streetcar line feeding into it was replaced by bus service, and Pleasant Street Portal at its southern end has been covered over. Reuse of part of the tunnel for the Silver Line Phase III was briefly considered, but the narrow bore was found too small for the Silver Line buses which (unlike trolleys) are not fixed to their guideway. Plans for the Phase III tunnel were shifted further west to new alignments, then canceled due to questions over the project's cost-effectiveness. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Green Line (MBTA)」の詳細全文を読む スポンサード リンク
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