Virginia closed a deal with private companies to build $925 million express lanes along Interstate 95, Gov. Bob McDonnell announced Tuesday.

The high-occupancy toll lanes -- or HOT lanes -- could be used for free by drivers with two or more passengers, but other drivers would be charged a fee. HOT lanes would replace current carpool lanes. The lanes will stretch 29 miles from Garrisonville Road in Stafford County to Edsall Road in Fairfax County. Construction will begin in August.

"The project will bring transportation choices to commuters traveling to and from the Northern Virginia region," Virginia Department of Transportation Commissioner Gregory Whirley said in a statement.

The two companies building the lanes, Fluor and Transurban, will also add and expand commuter parking lots along the highway. The companies also will maintain the roads. In exchange, they will keep most of the toll proceeds for 76 years.

The two companies will pay $854 million to build the lanes, including $300 million in an anticipated low-interest loan from the federal government. Virginia will pay $71 million -- less than the original estimate of $97 million.