The opening of the Medford Branch of the Boston Green Line Extension (GLX) today completes an important rail link in Greater Boston, representing a critical achievement for the Massachusetts Bay Transportation Authority’s (MBTA) regional transit system. Forecast to add 50,000 daily passenger trips to Boston’s transit network, the $2.3b project brings much-needed transit service to the Medford and Somerville communities.

As Design Professional for the GLX since 2016, Arup supported the MBTA with overseeing the design development, and testing and commissioning processes of the entire extension, including the Medford and Union Square branches. Altogether, the project includes the construction of 4.7 miles of new light rail tracks, the addition of six new stations, along with the relocation and reconstruction of Lechmere station, three new traction power sub-stations, a new vehicle maintenance facility, and a community path extension for cyclists and pedestrians that follows the length of the GLX route. The second of the GLX’s two segments, the Medford Branch follows the March 2022 opening of the Union Square Branch.

“Through close collaboration with the MBTA and MassDOT, we’re thrilled that Arup could help deliver a modern and sustainable rail line that helps Boston meet its carbon neutrality goals while improving accessibility and overall passenger experience,” said Jeff Tubbs, Principal and Project Director, Arup.

Arup was initially engaged by the MBTA as a consultant at a pivotal juncture of the project in 2015, when the increasing costs over previous estimates jeopardized the project’s continuity. Arup helped the MBTA generate a revised project scope, budget, and schedule, and initiated a design-build process. This allowed the long-delayed project to move forward, with costs cut by roughly $700 million.

The extension provides a critical rail link connecting Downtown Boston to both Union Square in Somerville and College Avenue in Medford, two densely populated and historically underserved areas. Primarily located in Somerville, the GLX brings 80% of the Somerville population to within walking distance of rail transit, compared to the previous 20%.

Alongside the GLX route, a multi-use community path provides access between stations in Somerville and the surrounding streets. This integral component also creates a safe, continuous route from Somerville to the Charles River and Downtown Boston – a key link to the city’s ongoing investment in accessible and safe biking infrastructure as a viable transportation alternative.

Daily vehicle trips will be cut by approximately 25,700 miles, significantly reducing associated air emissions. The GLX completion puts Boston one step closer to meeting its 2050 goal of carbon neutrality.