MBTA Green Line Light Rail Extension

Client: Massachusetts Bay Transportation Authority (MBTA)
Location: Boston, MA, U.S.

Executive Summary

The Massachusetts Bay Transportation Authority (MBTA) selected a Fluor-led joint venture as the design-build team for the Green Line Light Rail Extension in Boston, Massachusetts.

The 4.7-mile extension was completed in 2022 and will improve mobility for Boston-area residents.

Client's Challenge

The project comprises seven new stations, including the relocated Lechmere Station and a vehicle storage and maintenance facility. The extension includes two distinct branches: a mainline branch operating within the existing right-of-way for the MBTA Lowell Line beginning at Lechmere Station in Cambridge and traveling north to Medford, and a branch line operating within the existing right-of-way for the MBTA Fitchburg Line to Union Square in Somerville.

The light rail service to this corridor will address longstanding area transportation concerns, offering a one-seat ride to downtown Boston, resulting in fewer automobiles on local roads and a reduction in greenhouse gas emissions and other components of air pollution.

The Green Line Extension (GLX) will also support municipal plans for sustainable growth and urban redevelopment, providing residents with greater transportation access to jobs and other destinations.

Fluor's Solution

Green Line Extension Constructors, the Fluor-led joint venture, is overseeing the design and construction of the Green Line Extension. The joint venture brings significant design-build and transit experience, as well as successful completion of prior work for the MBTA.

The team developed several technical concepts to improve cost and schedule certainty while maintaining quality, designed to result in increased service life, reduced maintenance and improved accessibility and public safety. The team has also integrated local vendors, subcontractors and service providers, as well as engaged disadvantaged and minority-owned business enterprises.


Construction on the project began in 2018. The Union Square Branch of the Green Line Extension opened in March 2022. This 0.7-mile line was the first of two distinct branch lines to open as part of the project, running from the new and relocated Lechmere Station in Cambridge to Union Square in Somerville. The addition of the Union Square station provided first-time access for those in the City of Somerville just north of Boston.

The second line of the 4.7-mile project, the four-mile mainline branch, opened in 2022. It includes the addition of a large vehicle storage and maintenance facility and the extension of the community path from Somerville into Cambridge.

The projected daily ridership at the seven stations is estimated to be 45,000 by 2030.