State officials announced Thursday that they had signed a $1.4 billion deal to build a highway in southeastern Virginia, prompting criticism from those who say the state’s scarce transportation resources should be spent in more heavily traveled corridors.

Gov. Robert F. McDonnell (R) has pushed for the road since he represented the region as a state delegate.

“As recognized by local officials and the General Assembly years ago, there is a clear and critical need for the new U.S. 460,” McDonnell said in a statement announcing that the state had signed a contract with US 460 Mobility Partners, a partnership of Ferrovial Agroman and American Infrastructure.

The highway will extend for 55 miles between Petersburg and Suffolk, running parallel to U.S. 460, a four-lane road along which average volumes range from 9,200 to 17,000 vehicles a day. The state estimates that the new highway, a toll road that will not replace the existing toll-free route, will initially carry 5,000 to 6,000 cars and trucks a day.

Critics of the project say the traffic projections are too low to justify the $1.4 billion investment. They include all three Democrats representing Virginia in the U.S. House of Representatives, who wrote a joint letter this week trying to head off the deal.

A map of the proposed toll road for Route 460

At a time when the state is on track to run out of road funds by 2017, some would like to see the money spent on projects to alleviate congestion in Hampton Roads or Northern Virginia.

“He calls himself a fiscal conservative when he is flushing $1.4B of [taxpayers’] money down the toilet on a worthless project that very few people support and even less people will use,” Sen. Minority Leader Richard L. Saslaw (D-Fairfax) said of McDonnell in an e-mail.

State officials say the highway will provide an alternative to jam-prone Interstate 64 for vehicles traveling between Suffolk and Richmond.

But they primarily tout the project as a means of economic development, one that could help the state capi­tal­ize on the expansion of the Panama Canal. They say the highway will spur construction of huge freight-distribution centers that will enhance the appeal of the nearby Port of Virginia, which has channels deep enough to accommodate the enormous“post-Panamax” ships expected to start passing through the canal in 2015.

The planned highway is commonly referred to as the “new 460,” although it has not been decided whether it will assume the old route number or get a new one.

Reps. Gerald E.Connolly, James P. Moran and Robert C. “Bobby” Scott — all Virginia Democrats — sent a letter to McDonnell, the Federal Highway Administration and the Army Corps of Engineers, urging them to delay execution of the contract.

The Virginia Department of Transportation’s “underwhelming traffic projections for the project are of particular concern considering the transportation funding challenges we face at both the Federal and State levels,” the letter says.

The letter also notes concerns about the possibility of wetlands destruction, an issue that the Army Corps of Engineers has raised in connection with the project.