The Green Line Extension (GLX) is a construction project to extend the light rail Massachusetts Bay Transportation Authority (MBTA) Green Line northwest into Somerville and Medford, two inner suburbs of Boston, Massachusetts. The project begins at the north end of the Lechmere Viaduct, where the former ground-level Lechmere station was replaced by an elevated station on an extended viaduct. An extension of service beyond Lechmere was considered as early as 1922, with the first formal proposal in 1926. Despite appearing in other regional plans throughout the 20th century, the state did not commit to the project until 1990. Planning began in 2006 with a projected completion date of 2014; this was delayed to 2015, then to 2018. A groundbreaking was held in 2012, with several early construction elements over the next two years. In 2015, with projected costs increased to $3.3 billion, the project was placed on hold. A revised plan, with more modest stations and other value engineering, was submitted in 2016 and approved in 2017. The main $1.08 billion design-build contract was issued in November 2017, with several optional items like platform canopies and a larger vehicle maintenance facility included. Construction began in 2018, with the old Lechmere station closed in May 2020. The new Lechmere station and Union Square Branch opened on March 21, 2022, with the Medford Branch expected to open in late summer 2022.
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