Green Line Extension tests first trains

Trains are finally rolling on the Green Line Extension, marking an achievement many years, delays, and budget increases in the making.

“This is really the biggest milestone of the project to date,” said state Rep. Mike Connolly, D-Cambridge. “So many of us, for years, have advocated and sometimes even had to struggle to try to keep the project alive, and so to now see these new light rail vehicles pulling into Union Square Station and Lechmere Station, that really makes it real, and it’s just a beautiful sight to behold.”

On Friday morning at 8:00 a.m., the test trolleys — without passengers — slowly but successfully made their way from the Vehicle Maintenance Facility to the new Lechmere Station, ending at Union Square Station. The Union Square branch in Somerville is slated to open in March 2022. The Medford branch, which will make stops in East Somerville, Gilman Square, Magoun Square and Ball Square before ending in Medford near the Tufts University campus, will open in May.

An MBTA spokesperson said that the T will use all three current Green Line trolley models to test tracks, switches and the overhead catenary system over the next several months. Trolley operators will also use the time to train on the tracks and familiarize themselves with the GLX infrastructure, including its stations and platforms.

Connolly, who was a GLX advocate before he took office in 2017, said that the project will “dramatically improve transit access in both directions,” he said, allowing Cambridge residents to T to Somerville and Medford, and will especially expand transit for Somerville and Medford residents to the rest of the metro area.

To sweeten the deal, Somerville and Cambridge will both be paid back in full for their financial contributions to the project. Somerville contributed $50 million and Cambridge contributed $25 million.

Outgoing Somerville Mayor Joseph Curtatone rattled off statistics of how GLX will shape the area, taking 25,000 cars off the road, creating 10,000 new homes in the region and 30,000 new jobs, and generating $3 billion in new economic activity, especially in Kendall Square, which he said will ultimately benefit the entire Commonwealth.

“It’s really the best light rail project on the books in generations,” he said.

PAUL cONNORS / bOStON heRALd WORK IN PROGRESS: MBTA Green Line Extension tracks pass underneath the Cross Street bridge, as seen from the McGrath Highway bridge on Saturday in Somerville.