The Union Square Branch opening of the long-awaited Boston Green Line Extension (GLX) marks a major milestone for the Arup-supported project. 

The first of two segments as part of a 4.7-mile extension of the Massachusetts Bay Transportation Authority’s (MBTA) regional transit system, the Union Square Branch comprises the new Union Square and Lechmere stations. The opening of the Medford Branch later this year will conclude the development of this decades-long project. 

The GLX is expected to add 50,000 daily passenger trips to Boston’s transit network and bring much-needed service to the Somerville, Cambridge, and Medford communities. The project will also help bring the city closer to meeting its 2050 goal of carbon neutrality by significantly reducing vehicle-related emissions. 

Arup is serving as the project’s Design Professional, supporting the MBTA with overseeing the design development, and testing and commissioning process. The firm was first tapped by the MBTA as a consultant in 2015 when the additional cost of the project surpassed $1 billion jeopardizing the initiative’s continuation. Arup helped generate a revised project scope, budget, and schedule, and initiated a design-build process. This resulted in the delayed project to cut costs by roughly $700 million. 

"The opening of this first segment of the Green Line Extension is a testament to the incredible collective efforts and coordination between Arup, the MBTA GLX leadership, MassDOT, and the overall GLX project team," said Jeff Tubbs, Arup principal and project director.

Located primarily in the historically underserved Somerville area, the GLX will bring 80% of the city’s population within walking distance of rail transit, compared to the current 20%. The GLX is already helping to spur economic development in the area with numerous new commercial, residential, and civic projects under development. When complete, it will feature seven new stations and three new traction power substations, and an additional two miles of community path.