Providence Line
Readville station
Providence Line platforms in the foreground, with a complex ramp system to cross the tracks and access the Franklin Line and Fairmount platforms; in the distance, the blue overpass carries the Midland Route over the Shore Line — used by a small number of Franklin trains when slots are unavailale on the Southwest Corridor into South Station
Readville station
I am convinced that the original structure here was at least a two-track bridge; the second Dorchester Branch track ends at a bumper block just out of frame to the left, and the double-track resumes at SPRAGUE interlocking a short distance down the line. (If you're finding yourself confused, that's not unreasonable: all of the railroad lines in Massachusetts have been renamed by practically every railroad to use them. This track was the Midland Route to the New Haven, the Dorchester Branch to Conrail, and the Franklin Line to the MBTA; the line below was the Shore Line to the New Haven, the Northeast Corridor to Amtrak, the Southwest Corridor to the city of Boston, and the Providence/Stoughton Line to the T.)
Readville station
Track 5 serves the lion's share of Franklin Line trains, which follow the Southwest Corridor so that they can call at Ruggles (for Longwood Medical Area workers) and Back Bay, which the historic Midland Route does not serve. In a Regional Rail service model, all Franklin trains would use the Dorchester Branch and have a regular timed transfer with the Providence Line, and this platform would go unused.
Mansfield station
This $7 million construction project (which was not yet finished when I took these pictures) angered a lot of activists, and resulted in the federal government finally putting its foot down, because the MBTA approved a design for completely new low-level platforms with mini-highs, claiming that STRACNET clearances prevented construction of full-length high platforms. The main aim of the project was to build an accessible path of travel between the inbound and outbound platforms — the station had had mini-highs before but there was no way to get from here to the parking lot on the other side of the tracks. (I'm standing on the end of one of the wooden temporary mini-highs used during platform construction.)