The Hartford Line is a commuter rail service between New Haven, Connecticut, and Springfield, Massachusetts, using the Amtrak-owned New Haven–Springfield Line. The project is a joint venture between the states of Connecticut and Massachusetts, with support from the federal government as well. CT Rail-branded trains provide service along the corridor, and riders can use Hartford Line tickets to travel on board most Amtrak trains along the corridor at the same prices. The service launched on June 16, 2018.

The passenger locomotives derivatives of the General Motors EMD GP40 diesel-electric locomotive have been, and continue to be, used by multiple passenger railroads in North America. For passenger service, the locomotives required extra components for providing steam or head-end power (HEP) for heating, lighting and electricity in passenger cars. Most of these passenger locomotives were rebuilt from older freight locomotives, while some were built as brand new models.