Since construction began in 2018, the Medford branch of the Green Line will open on Dec. 12, announced MBTA General Manager Steve Poftak at Thursday’s board meeting. 

The branch, which services College Avenue, Ball Square, Magoun Square, Gilman Square, and East Somerville stations, will be used by over 50,000 daily riders. 

The opening of the Medford line—part of the $2.3 billion Green Line Extension—will complete the project. The first phase of the project finished in March, which extended the Green Line from Lechmere to Union Square, relocated Lechmere Station in Cambridge, and build a brand-new Union Square Station in Somerville. 

The announcement follows several delays since the commencement of the project in 2018. Both the Union Square and Medford branches were set to open in December 2021 but COVID-19 caused delays. Last year, the MBTA cited complications in building substations for the Union Square extension and supply chain issues for the Medford extension. The agency most recently projected the Medford branch would open in late November. 

“We had some additional work we wanted to get done. We also wanted to be sure we were doing everything we needed to do, not only on the Medford Branch but across our system,” Poftak said at the meeting. “We’re taking a few extra days, but we will open at the beginning of service on Dec. 12.”

The MBTA Board of Directors also unanimously approved a revised bus network, which aims to increase service to riders in and around Boston. The plans will be implemented in stages from 2023 to the end of 2028.