About the Green Line Extension Project

The Green Line Extension (GLX) project extends the existing MBTA Green Line north from Lechmere Station to further service in Somerville, Cambridge, and Medford. The Union Square Branch opened for passenger service on March 21, 2022. The Medford Branch began passenger service on December 12, 2022.

Table of Contents


  • A one-seat ride from the project corridor to downtown Boston, (eliminating the need for bus and rail transfers at Lechmere Station and at Orange and Red Line stations) improving travel times within the project corridor.
  • A projected reduction in regional daily Vehicle Miles Traveled by 25,728 miles, improving air quality and reducing automobile congestion.
  • Daily ridership (boardings and alightings) at the seven Green Line Extension stations of approximately 45,000 by 2030. The majority of those trips will be made beginning in the first year of service on the Green Line Extension.
  • A commitment to universal access, with new stations that will meet or exceed the Americans with Disabilities Act (ADA) standards.
  • Operation in existing railroad rights-of-way, reducing the need to purchase local property and minimizing construction impacts.
  • Mitigation measures that will reduce existing noise and vibration impacts from area railroads.

Contract Status

The GLX "Phase 1" construction contract (E22CN01) is complete. Work included the reconstruction of the Harvard Street Railroad Bridge in Medford and the Medford Street Railroad Bridge in Somerville as well as the demolition of the MBTA-owned facilities at 21 Water Street in Cambridge.

The Interim Guaranteed Maximum Price (IGMP) construction contracts (E22CN02, E22CN03, E22CN04, and E22CN06) are in the close-out phases. Work included the procurement of long lead items, utility relocations, drainage improvements, and track infrastructure.

The MBTA has retained a Design Professional (DP) in accordance with the requirements of Massachusetts General Law Chapter 149A, Section 18. The DP is responsible for the overall management of all technical and design aspects of the Design Build procurement, design, and construction phases of the GLX program.

The procurement process for the GLX Design Build contract was completed on December 20, 2017 with the issuance of Notice to Proceed (NTP) to the Design Build Entity selected in a Bid Opening on November 17, 2017 and accepted by the MBTA Fiscal & Management Control Board on November 20, 2017. Today, design work is complete, and the project is in the final stages of construction. During peak construction, approximately 650 daily personnel supported the project effort. The GLX Union Branch opened for passenger service on March 21, 2022, and the Medford Branch began passenger service on December 12, 2022.

Additional Resources

FTA Participation

On January 5, 2015 a Full Funding Grant Agreement (FFGA), between the MBTA and the U.S. Department of Transportation Federal Transit Administration (FTA) was signed that establishes the scope of federal participation in the GLX project. Under the FFGA, federal dollars will fund approximately $996 million of the newly revised budget of $2.28 billion.

On April 3, 2017 the FTA issued a report that provided concurrence on the MBTA's revised cost and schedule estimate for the GLX program. The MBTA also provided the FTA with an update to the finance plan on June 5, 2017. These are key milestones toward ensuring continued federal participation in GLX.

Environmental Approvals

State-level environmental review (MEPA) was completed in July 2010. Federal-level environmental review (NEPA) documents were submitted to FTA in September 2011, and a public hearing was held on October 20, 2011 (to accompany a 45-day public comment period).

A Finding of No Significant Impact (FONSI) was issued by FTA on July 9, 2012. The July 2012 issuance of the FONSI completed the federal-level environmental review process. Federal environmental clearance is the culmination of several years of technical work done by MassDOT and the MBTA with close cooperation from the Cities of Cambridge, Somerville, and Medford, as well as the participation of hundreds of individuals and local organizations.

On January 31, 2017, the MBTA filed a Notice of Project Change (NPC) for the Green Line Extension Project with the Executive Office of Energy and Environmental Affairs (EEA).

On March 10, 2017, the Executive Office of Energy and Environment issued a Certificate on the MBTA's Notice of Project Change for the GLX project

Additional Resources

Notice of Project Change on Extension of the Green Line to Mystic Valley Parkway

On October 17, 2017, the MBTA filed a Notice of Project Change (NPC) for the Green Line Extension Project with the Executive Office of Energy and Environmental Affairs (EEA). This NPC was noticed in the November 8, 2017 edition of the Environmental Monitor. Comments were accepted by EEA until December 12, 2017.

Additional Resources

Project Area Map

Click on station icon to view more information including:

  • Location information
  • Site plan
  • Station design

Project area map showing Cambridge, Somerville and Medford



MBTA Customer Support (617) 222-3200

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Mon-Fri (6:30am-8pm) and Sat & Sun (8am-4pm)


Green Line Extension inquiries info@glxinfo.com


200 Inner Belt Road
Somerville, MA 02143

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