The Red Line is standard gauge heavy rail.
Trains consist of mated pairs of electric multiple unit cars powered from a 600 V DC third rail.
All trains run in six-car sets.

Rolling stock is maintained at the Cabot Yard in South Boston.
Yard leads connect to the mainline at Columbia Junction, just north of JFK/UMass station.
Trains are also stored at Braintree (Caddigan Yard), Ashmont (Codman Yard), and Alewife.
Eliot Yard, on the surface near Harvard Square, served East Boston Tunnel cars for a short time and Red Line cars until it was demolished in the 1970s. (
East Boston Tunnel cars accessed the yard through the now-closed Joy Street portal near Bowdoin station and a track connection on the Longfellow Bridge).
The Red Line is standard gauge heavy rail. Trains consist of mated pairs of electric multiple unit cars powered from a 600 V DC third rail. All trains run in six-car sets.
Rolling stock is maintained at the Cabot Yard in South Boston. Yard leads connect to the mainline at Columbia Junction, just north of JFK/UMass station. Trains are also stored at Braintree (Caddigan Yard), Ashmont (Codman Yard), and Alewife. Eliot Yard, on the surface near Harvard Square, served East Boston Tunnel cars for a short time and Red Line cars until it was demolished in the 1970s. (East Boston Tunnel cars accessed the yard through the now-closed Joy Street portal near Bowdoin station and a track connection on the Longfellow Bridge).
Red Line (MBTA)