The MBTA Orange Line now reaches 55 mph between Oak Grove and Assembly after track improvements restored original design speeds. Photo: MBTADuring its August Board Meeting, the Massachusetts Bay Transportation Authority (MBTA) announced that Orange Line trains will be able to reach 55 mph on select portions of the line starting August 24, 2025. According to an agency release, the previous maximum speed on the Orange Line was 40 MPH. This is the first time it has been documented that the Orange Line reached 55 mph. "General Manager Eng and his team are continuing to deliver for MBTA riders.