page_title: Massachusetts Bay Transportation Authority
section_title: Green Line
hierarchical_section_title: Massachusetts Bay Transportation Authority / Funding / Projects underway and future plans / Green Line
context_page_description: The Massachusetts Bay Transportation Authority is the public agency responsible for operating most public transportation services in Greater Boston, Massachusetts. Earlier modes of public transportation in Boston were independently owned and operated; many were first folded into a single agency with the formation of the Metropolitan Transit Authority in 1947. The MTA was replaced in 1964 with the present-day MBTA, which was established as an individual department within the Commonwealth of Massachusetts before becoming a division of the Massachusetts Department of Transportation in 2009.
  The MBTA and Philadelphia's Southeastern Pennsylvania Transportation Authority are the only US transit agencies that operate all five major types of terrestrial mass transit vehicles: light rail vehicles; heavy rail trains; regional rail trains; electric trolleybuses; and motor buses. In 2016, the system averaged 1,277,200 passengers per weekday, of which heavy rail averaged 552,500 and the light-rail lines 226,500, making it the fourth-busiest subway system and the busiest light rail system in the United States.
context_section_description: To settle a lawsuit with the Conservation Law Foundation to mitigate increased automobile emissions from the Big Dig, the Commonwealth of Massachusetts agreed to extend the Green Line north to Somerville and Medford, two suburbs currently under-served by the MBTA. This plan starts at a relocated Lechmere station, and terminates at College Avenue in Medford and Union Square in Somerville.  The original settlement-imposed deadline was December 31, 2014. There will be an expected daily ridership of 8,420. After projected costs increased to $3 billion, the project was halted in 2015 and scaled back. The revised project broke ground in June 2018 and is expected to serve passengers beginning in late 2021.
  Another mitigation project in the initial settlement was restoration of service on the E branch between Heath Street and Arborway/Forest Hills. A revised settlement agreement resulted in the substitution of other projects with similar air quality benefits. The state Executive Office of Transportation promised to consider other transit enhancements in the Arborway corridor.
caption: Map of the Green Line Extension (GLX).