Amtrak provides an additional eight New Haven-Springfield round-trips, two of which were added to the schedule upon launch of the Hartford Line in June 2018.

This makes for a total of eighteen round-trips between New Haven and Hartford, fourteen of which operate the full line to Springfield.

[23] The 16 cars were operated in four-car consists in a push-pull configuration with GP40-3H locomotives transferred over from Shore Line East.

[24] The railcars required significant repair and repainting before entering service, leading the Connecticut DOT to request $2.3 million from the state legislature in April 2018.

[37] In 1994, the Connecticut Department of Transportation (ConnDOT) conducted a feasibility study for a New Haven–Hartford service which envisaged three trips in the morning and three in the afternoon.

This would require $249 million in capital costs, both for rolling stock and to restore double tracking to the line.

Although reestablishing service was briefly mentioned in the South Central Regional Council of Government's January 2001 Long Range Mobility Plan,[39] it was not until 2003 that the commuter service provision began to be consistently listed among key transportation priorities in the annual Greater New Haven Chamber of Commerce Legislative Agenda.

[40] The New Haven–Hartford–Springfield Commuter Rail Implementation Study, released in 2005 by ConnDOT, recommended half-hour peak service, with new stations at North Haven/Hamden, Newington, and Enfield.

No action was taken following the study, as proposed schedules did not link well with those of the New Haven Line and ridership projections were low (particularly for northbound morning and southbound evening trips).

[24] In January 2010, $40 million of stimulus funds were approved to double-track 10.5 miles (16.9 km) of the corridor under the American Recovery & Reinvestment Act.

[43][44] In July 2010, Governor Jodi Rell asked the Connecticut State Bond Commission to authorize borrowing $260 million in an effort to attract additional federal matching funds, to double-track the remainder of the corridor, construct freight sidings, and improve signaling.

[47] As of April 2011, Connecticut State officials had applied for $227 million from the federal government that would complete track improvements between Hartford and Springfield, Massachusetts.

ConnDOT applied for the money to the Federal Railroad Administration, part of $2.4 billion that Florida governor Rick Scott rejected because of the spending it would require from his budget.

[50][51] If further funding is found to build these additional miles, it would complete the double-tracking of the line except for downtown Hartford and the aging Warehouse Point railroad bridge.

[53] The state intends to seek FRA funds to pay for construction of the new and rebuilt stations, the replacement of the Warehouse Point bridge, and a layover yard near Springfield.

[56] On August 3, 2015, Amtrak began busing its weekday morning and evening New Haven–Springfield Shuttle trains to allow double tracking work to begin.

[56] On October 11, 2016, a 17-car track-laying train began work to build the second track on the southern half of the line.

[72] In January 2025, ConnDOT was awarded an $11.6 million federal grant that will fund additional service including extension of some weekend trains to Windsor Locks.