Boston Engine Terminal (or BET, as everyone refers to it) is the MBTA's northside commuter rail maintenance facility.  It handles all the repair work for the northside fleet, and does much of the work for the southside fleet as well.  Equipment from the southside is transferred to BET every night from Readville via Beacon Park and CSX's Grand Junction Branch through Cambridge.  BET can perform most of the maintenance needed by the commuter rail fleet, with the exception of overhauls, body work, and other heavy maintenance, which are handled by outside contractors.

BET sits inside a large wye.  To the south is the Fitchburg Line; to the east and north, the Lowell, Haverhill, Newburyport and Rockport lines; and to the west, the Grand Junction Branch (which continues up to Chelsea) and several tracks used by the T and Pan Am (the T uses a pair to store maintenance of way (MOW) equipment, Pan Am uses another pair for staging BO-1, the local switcher).

The current BET was built in the mid-1990s to replace a steam-era Boston & Maine facility.  Between the building and the Fitchburg Line is Yard 14, used for storing out-of-service equipment and off-duty trainsets, and overlooked by Tower H.  Sixteen tracks run into the building, with all but the last three running all the way through.  Tracks 1-3 (on the south end of the buidling) are the Service & Inspection (S&I) tracks, which include the wash racks.  Tracks 4 and 5 are the Preventative Maintenance (PM) tracks.  The S&I and PM tracks handle cleaning and light maintenance.  Track 6 is the wheel machine track, which trues the wheels on coaches and locomotives.  Tracks 7-10 are the Diesel House, which handles locomotives.  Tracks 11-13 are the Coach House, which handles coaches.  Tracks 14-16 are the backshop, and are the only ones that don't run through the building.  The backshop handles heavier repairs, such as truck/wheel changeouts, prime mover changeouts, and so on.  The northern-most part of the building has the parts warehouse and offices for the T and Massachusetts Bay Commuter Rail.

I worked for MBCR several summers starting in 2004 and ending in 2007.  During that time, I was able to take photographs all over the facility.