The Greenbush Line is a branch of the MBTA Commuter Rail system which serves the South Shore region of Massachusetts.

The New Haven had plans to electrify some southside commuter lines, and some infrastructure was built, including lower-level loop platforms at South Station.

However, the third rail was dangerous at grade crossings, and the South Shore returned to steam-only service in 1902.

[6] Under the control of the New Haven Railroad, the South Shore Line and others set all-time records for number of passengers.

The number of daily trips was increased from 4 to 8 after World War II under Frederick C. Dumaine, Jr., and modern diesel trains including Budd RDCs were introduced in the 1950s.

[5] Freight trains continued to use the line as far south as the Hingham Lumber Yard located, where the Nantasket Junction station now exists, until 1979.

[7] Concerns were also raised about traffic jams being created at the grade crossings while the gates were down for trains to pass.

[9] Partially as a result of extensive litigation, the MBTA then worked with the towns along the Greenbush route to enact several measures to mitigate the environmental impact of the restored train service.

These included constructing an 890-foot (270 m) long tunnel costing $40 million under downtown Hingham, another trenched underpass at Weymouth Landing, and the soundproofing of homes and businesses located near the railroad tracks.

The line was built with 3,100 parking spaces, and was eventually expected to provide 8,600 one-way rides daily, diverting approximately 5,000 of those trips from automobiles.

[10] The Greenbush Line opened for regular passenger service on October 31, 2007, with 12 round trips on weekdays and 8 on weekends.

Each station has 200 to 500 parking spaces, except for Greenbush, which houses 1000 spots in order to serve commuters driving from Hanover, Norwell, Marshfield, and Duxbury.

By 2010, despite predictions of 4,200 inbound passengers a day (or 8,400 total daily one-way trips) riding the train by three years after its opening, the MBTA said that ridership was only half that.

The move came as a part of fare increases and service cuts in order to close the agency's operating budget shortfall for the following year.

[18] Substantially reduced schedules due to the COVID-19 pandemic were in effect from March 16 to June 23, 2020, and from December 14, 2020, to April 5, 2021.