Toll-Lanes Contract Could Cost State

"This is a way to get a significant amount of relief at a pretty modest cost to the state," said Poole, who tracks developments in the private toll-road arena. Also, "it's in the interest in both parties to ensure a good revenue stream."

Poole said that if the HOT lanes are flooded with motorists who don't pay tolls, "then it doesn't work."

Adding HOT lanes to the Capital Beltway, already one of the busiest highways in the country, is unprecedented in its ambition. In addition to building four lanes largely in the existing footprint of the Beltway, the builders had to figure out ways to get customers quickly in and out of job centers and such destinations as Tysons Corner, the Dulles Toll Road, the Springfield interchange and Route 66.

Fluor-Transurban is negotiating with the state to convert and expand the two reversible high-occupancy vehicle lanes on Interstate 395/95 into three reversible HOT lanes. Carpoolers and sluggers are concerned that the change would upset the successful system that has evolved on the highway over the years.

Ronald F. Kirby, transportation director for the Metropolitan Washington Council of Governments, said that once the Beltway HOT lanes connect with HOT lanes planned for I-395/95 and the HOV lanes on the Dulles Toll Road and I-66, drivers would realize that piling three people into a car could provide a free rocket ride across the region.

"I don't have any numbers to say that their numbers are too high or too low," Kirby said. "We don't have any experience with a facility like this."

But he said the "network effect" could provide greater incentives to carpool and perhaps trigger much larger carpool payments than state officials estimated. "There is some assumption of risk on the part of the state here."