From South Junction/Tower 1 (MP 228.5/0.0), four tracks continue south-southwest, bridging over the Fort Point Channel, while five tracks curve west, CETC, overhead electrification, with speed limit 15 mph for passenger trains and 10 mph for freights, past two sets of four road bridges overhead for the Interstate Highway junction, a spur trailing in from the south, Cove (MP 228.0/1.1), west end of the wye at South Junction, where the two former Conrail Boston Line tracks (no electrification) separate from the three electrified Amtrak Main Line tracks, all with speed limit 30 mph) as both head just north of due west, a road bridge overhead, the line down in a trench, with the MBTA Orange Line alongside to the north, and the passenger station with two side platforms beneath an air-rights building above, with the two side platforms of the Orange Line alongside to the north, at Back Bay (MP 227.6/1.2), west of which, in the "tunnel" formed by the air-rights construction overhead, the Amtrak line swings south-southwest while the former Conrail line continues just south of due west.