On the morning of October 30th, 2024, a set of new CRRC-built "#4 Red Line" cars sits at the Vehicle Testing Facility on the Red Line Test Track adjacent to the South Boston Bypass in Boston, Massachusetts. These cars are slowly replacing the aging #1, #2 and #3 Red Line cars. The Red Line Test Track uses a portion of the South Boston Waterfront Industrial Track (Track 61) right-of-way that was abandoned by CSX several years ago.