This project will restore commuter rail service on the existing right-of-way known as the Greenbush corridor through the towns of Braintree, Weymouth, Hingham, Cohasset and Scituate, Massachusetts. The project begins at the connection with the existing MBTA Old Colony Main Line at the Braintree Wye in East Braintree, and extends 18 miles easterly along the former New Haven Railroad Greenbush Branch to the terminus in the Greenbush section of Scituate. The project involves the reconstruction of existing, largely out-of-service railroad right-of-way as a single track railroad with four controlled passing sidings of approximately 1 mile in length each. Once completed, the facility will be equipped with a new signal and communications system and end-of-the-line train layover facility. In addition, certain freight facilities in Braintree will be relocated off-line.

The right-of-way is currently active for local freight service on the first 1.5 miles in East Braintree. The remainder of the right-of-way is either out of service or abandoned. The proposed commuter rail service will provide twelve (12) round trips between Boston-South Station and Greenbush each weekday and eight (8) round trips on weekends. Scheduled peak-direction one-way trip time between South Station and Greenbush, including a stop at Quincy Center, will be 59 minutes.

Seven new commuter rail stations will be constructed along the right-of-way, each with an 800-foot long high-level platform. New commuter parking lots at the stations ranging in size from 200 to 1000 spaces each will provide a total of approximately 3000 spaces corridor wide. Stations will be similar to those constructed on the other Old Colony lines and will include accommodations for bicycle parking and passenger drop-off/pick-up by automobile, van, or bus.

Nine existing single span railroad bridges will be reconstructed with new ballast deck superstructures and new or rehabilitated abutments and wing walls. Work will be performed on two existing roadway bridges over the right-of-way: one (1) bridge will be replaced in its entirety and the other will be repaired. Four (4) new grade separations will be constructed: at Weymouth Landing (shallow cut tunnel); Green Street (new railroad bridge over lowered roadway); Hingham Square (underpass with 800 foot long cut and cover tunnel crossing under three (3) roadways); and Rocky Lane (new highway bridge on new roadway alignment crossing over the right-of-way).

Of the forty-three (43) existing roadway grade crossings on the right-of-way, ten (10) will be closed and eight (8) eliminated by grade separations. The remaining twenty-five (25) crossings, plus one (1) new roadway crossing and three (3) pedestrian crossings, will be reconstructed with new grade crossing warning systems and supplemental safety measures in accordance with the Swift Act. The entire facility will be designated as a quiet zone (no routine use of train whistles at crossings). Intersection improvements will be made at locations immediately adjacent to the railroad and station entrances and at seven (7) remote locations. At one (1) location on Route 3A in Scituate, an existing signalized intersection will be replaced with a combination of traffic signals and a roundabout. New or modified traffic signals will be installed at a total of nineteen (19) locations.

The project includes extensive mitigation measures to address noise, vibration, historic, wetland, and other impacts. Noise barriers will be constructed at six (6) locations, vibration-dampening ballast mats will be installed under a total of 3.5 miles of track, and screen plantings will be installed along 6 miles of right of sidelines. Fencing, consisting of chain link, security, black chain link, solid wood, or steel picket, depending on location, will be provided along virtually the entire length of the right-of-way. Mitigation agreements have been reached with all five (5) Towns detailing specific mitigation items to be provided. In accordance with the Section 106 Agreement Resource Consultations, a Project Conservator will monitor the project to ensure that historic properties are protected and mitigated as agreed. An Independent Observer will monitor the Project to ensure that wetlands are protected and mitigated in accordance with certain environmental approvals. Additional mitigation measures, such as noise abatement of individual homes, will be performed by the MBTA directly.