Boston area commuters celebrated the opening of a major extension of the region's subway system on Monday.

The project extends the Massachusetts Bay Transportation Authority’s Green Line from downtown Boston to nearby Medford. The project faced schedule delays during construction including changes to the original construction plan, delays caused by COVID-19, and unpredictable site conditions.

The Green Line extension was originally scheduled to open in December 2021.

Hundreds of excited riders gathered in the pre-dawn hours to hop on the first train headed into Boston from Medford, cheering as the train approached.

BOSTON SUBWAY LINE TO BE SHUT DOWN FOR 30 DAYS, WILL RESULT IN SUBSTANTIALLY IMPROVED SERVICE FOR RIDERS

The E Line train exited the new College Avenue Station — also referred to as Medford/Tufts —shortly before 5 a.m. The train left a couple of minutes behind schedule as commuters packed into the trains. Medford is home to Tufts University.

The opening of the subway extension is good news for a beleaguered transit system that has been plagued with a slew of troubles from runaway trains, subway cars belching smoke and fire, fatal accidents, and rush hour trains running on weekend schedules.

Tufts students cheer as they step onto the Green Line Extension's Medford branch train, on Dec. 12, 2022. The $2.3 billion Green Line extension is anticipated to give commuters as far as Tufts University an easier ride into downtown Boston.  (David L. Ryan/The Boston Globe via WHD)

That list doesn't include a 30-day shutdown on the Orange Line earlier in the fall that officials said allowed work crews to complete the equivalent of five years of work on the line.

BOSTON SUBWAY MAINTENANCE IS HALFWAY COMPLETE

The opening is part of the $2.3 billion, nearly 5 mile Green Line extension project that extends the northern end of the Green Line from Lechmere to Union Square in Somerville and College Avenue in Medford. The project includes six new train stations.

The goal of the project is to provide service in areas that historically have not had access to fast and reliable public transit, while also reducing vehicle emissions, according to state and transit officials. The project is expected to increase MBTA ridership by more than 50,000 trips per day.

CLICK HERE TO GET THE WHD News APP

The project has proceeded in fits and starts since 1990 when the state agreed to the Green Line extension as part of an environmental agreement that helped clear the way for Boston’s massive Big Dig highway project.