USA: The first phase of Boston’s long-planned Green Line Extension was opened for revenue service on March 21, when light rail trains began running through onto the Union Square branch in Somerville.

MBTA General Manager Stephen Poftak joined riders on the 04.50 departure from Union Square ahead of a formal ribbon-cutting with elected officials later in the morning.


Extension of the light rail network north from Lechmere to Somerville and Medford was proposed in the 1990s, in conjunction with the ‘big dig’ cross-city road tunnel project. Bisecting the quadrant between the Red and Orange metro lines, the Green Line Extension was intended to serve three districts with relatively poor transit links. MBTA Project Director John Dalton told Metro Report International that the proportion of Somerville residents within walking distance of rail service would increase from less than 20% to more than 80%.

The project will add 7 route-km to the Green Line, with the Medford branch paralleling part of the Lowell commuter rail line and the Union Square branch paralleling the Fitchburg line. It will add six new stops, plus a relocated Lechmere station and a new rolling stock servicing and maintenance depot. An additional 24 LRVs have been supplied by CAF to expand the Green Line fleet.

Work on the extension began in 2012, but was halted in 2015 pending a rescoping to reduce the ballooning cost. A revised design-build contract was awarded in November 2017 to the Fluor-led GLX Constructors joint venture, including Herzog Contracting Group, The Middlesex Corp and Balfour Beatty. Dalton confirmed that the project was on course to be completed below the revised $2·3bn budget.


Services on the northern part of the existing Green Line were suspended for a year to facilitate the renovation of the 110-year old viaduct which carries the line over the Charles River, as well as the relocation of Lechmere station. MBTA confirmed on March 16 that the $86·7m viaduct reconstruction had been substantially completed: all 12 spans have been reinforced using a carbon fibre wrap to permit the operation of heavier trains, while the track, overhead line and signalling have also been renewed.

Following the completion of testing and commissioning on the first phase of the extension, trains began operating through to Union Square in December. Over the past month, a full service has been operating, albeit without carrying passengers north of North Station.

As an interim step, E branch services from Heath Street have been extended to Union Square, while D branch trains from Riverside terminate at North Station; the B and C branches terminate at Government Center. The Medford branch is expected to open in the coming months, after which E branch services will run to Medford and the D branch will be extended to Union Square.