Green Line Extension

Green Line Extension
source
Name	Green Line Extension
Type	Light rail
System	Massachusetts Bay Transportation Authority
Status	Operational
Locale	Middlesex County, Massachusetts
Start	Lechmere
End	Union Square / Medford/Tufts
Stations	7 new
Open	2022–2023
Owner	Massachusetts Department of Transportation
Operator	Massachusetts Bay Transportation Authority
Character	Grade-separated and at-grade
Linelength	4.7 miles (7.6 km)

Green Line Extension. The project is a major expansion of the MBTA Green Line light rail system in the Boston metropolitan area, extending service north from Lechmere station into the cities of Somerville and Medford. Constructed to fulfill commitments made during the Big Dig project to mitigate increased automobile traffic, it represents the largest expansion of the Massachusetts Bay Transportation Authority rail system in decades. The extension opened in two phases, with service to Union Square beginning in March 2022 and the branch to Medford/Tufts opening in December 2022.

Background and planning

The origins are deeply tied to legal and environmental mandates from the Central Artery/Tunnel Project. As a condition of federal approval, the Commonwealth of Massachusetts agreed to several transit improvements to offset air quality impacts, a commitment legally enforced by the Conservation Law Foundation. For decades, community groups like the Mystic View Task Force and the Somerville Transportation Equity Partnership advocated for its construction. Initial planning and environmental review, led by the Massachusetts Department of Transportation, progressed slowly, with a final Environmental Impact Statement approved by the Federal Transit Administration in the 2010s. The project was designed to provide high-quality transit access to densely populated, historically underserved areas and to support regional goals for sustainable development around new stations.

Construction and challenges

The initial construction contract was awarded to a joint venture led by White-Skanska-Kiewit in 2017, but the project faced a profound crisis in 2015 when cost estimates ballooned, prompting a redesign by the team of HDR and Arup Group. Under the leadership of MassDOT General Manager Stephanie Pollack, the project was radically value-engineered, simplifying station designs and altering the alignment near the Washington Street bridge. A new contracting model, using a Construction manager/general contractor method with GLX Constructors, was adopted to control costs. Major construction elements included building a new Lechmere station on a viaduct, constructing a maintenance facility in Somerville, and laying miles of new track through complex urban corridors alongside the Lowell Line and Fitchburg Line of the MBTA Commuter Rail.

Stations and service

The extension added seven new stations across two branches. The Union Square Branch terminates at Union Square station. The Medford Branch includes East Somerville station, Gilman Square station, Magoun Square station, Ball Square station, and terminates at Medford/Tufts station near the campus of Tufts University. All stations feature accessible, high-level platforms, public art installations, and connections to local bus routes like the MBTA bus network. Service is provided by the Type 9 and Type 10 fleets of MBTA Green Line vehicles, operating on headways comparable to the core subway sections. The project also rebuilt the historic Lechmere station, relocating it to a more central site in East Cambridge.

Funding and costs

The final project budget was approximately $2.3 billion, a figure stabilized after the 2015 redesign. Primary funding sources included a combination of state bond authorizations under the Chapter 90 program and critical grants from the Federal Transit Administration's Capital Investment Grant program. The Boston Region Metropolitan Planning Organization also allocated funds through its Transportation Improvement Program. Additional financial contributions came from the cities of Cambridge and Somerville, as well as assessments on major developers like DivcoWest in the NorthPoint area. The cost overruns experienced early in the process were a major subject of scrutiny by the Massachusetts State Senate and the Massachusetts Inspector General.

Impact and reception

The opening was celebrated by local officials including Somerville Mayor Katjana Ballantyne and Medford Mayor Breanna Lungo-Koehn, fulfilling a long-standing promise to the region. It has significantly increased Massachusetts Bay Transportation Authority ridership, providing reliable transit access to key destinations like Tufts University, Union Square, and the Brickbottom district. The project is expected to spur economic development and support the Commonwealth's goals under the Global Warming Solutions Act by reducing vehicle miles traveled. While praised for its eventual execution, the project's history remains a case study in the challenges of managing large-scale public works projects in the United States.

Category:MBTA Green Line Category:Railway lines opened in 2022 Category:Transportation in Somerville, Massachusetts Category:Transportation in Medford, Massachusetts