The Virginia Department of Transportation said yesterday that it would build high-occupancy toll lanes on a 14-mile stretch of the Capital Beltway, working with a private partner to create the first of an extensive network of the new-style highways for the Washington region.

The plan would add two lanes on each side of the Beltway, separated from other traffic, between Springfield and Georgetown Pike. The high-occupancy toll lanes -- or HOT lanes -- would be free for car pools of three or more people, but others would pay for the privilege of using them. To keep the lanes from clogging, tolls would increase with the amount of traffic.

"We want to build HOT lanes," said Virginia Transportation Commissioner Philip A. Shucet. "I think it could be one of the few options that we have to meaningfully improve mobility."

Virginia and Maryland leaders plan a network of congestion-priced highways that they say will unclog roadways in a region with the third-worst traffic in the nation. Virginia officials are considering additional HOT lanes on parts of Interstates 95 and 395, and Maryland officials are exploring plans to build them on the Beltway, I-270, the Baltimore Beltway and I-95 north of Baltimore.

Congestion-priced lanes are unusual now, but they are gaining favor across the nation as budget-strapped states look for ways to free drivers from daily jams. Officials in Texas and California proclaim the benefits of HOT lanes in their states, while Minnesota, Colorado, Washington and others are considering proposals.

Many details of the Virginia plan remain to be finalized, including the crucial issues of financing and access. Most of the construction cost will be paid by the private partner, Fluor Daniel, but the state's share has not been determined.

In addition, engineers need to work out which Beltway exits and entrances HOT lane drivers would have direct access to. Fluor officials say lanes could open in six years at the earliest.

Virginia officials said they sought private participation for the Beltway plan because the state does not have enough money on its own to widen the road any time soon. In return for its investment, Fluor would make a profit on construction and possibly receive a negotiated fee or a share of toll revenue, depending on how the two sides structure the financing.

Officials have embraced the concept as a way to give motorists relief from chronic tie-ups. They do not expect drivers to take HOT lanes every day, but they believe that everyone would use them sometimes. Occasional users might include parents who are late to pick up children from day care, business people who are rushing to meet clients, and fed-up commuters who simply want to get out of traffic.

"I'm all for it. I would gladly pay a premium," said Harry Dennis of Arlington, a lawyer who drives the Beltway almost every day. Dennis said he would have taken the Beltway yesterday to get from Reston to Springfield if it had HOT lanes, but because traffic is so unpredictable, he took back roads.

"It's such a crapshoot the way it is right now," Dennis said.

Backers also say the lanes would allow for bus service that Beltway traffic jams now make impractical. In addition, drivers on regular lanes would benefit when cars move over to the HOT lanes, supporters say.

Fluor's original $693 million proposal would require nearly $100 million in public funds, money that the state would have to shift from other projects. In May, an advisory panel of state transportation officials recommended changes to the plan, such as adding direct access to Tysons Corner, that would raise the price to as much as $840 million and the state's share to almost $250 million. Shucet said he is open to both approaches, and he has offered one of his own that would have Fluor pay the entire cost in exchange for permanent ownership of the road and all its toll revenue.

Shucet said the two sides also would consider broadening the proposal to include an $84 million link through the Springfield interchange.

Transportation analysts said the outstanding issues were not serious enough to keep the lanes from being built.

"I think there are still quite a bit of unresolved issues," said C. Kenneth Orski, editor of the Innovation Briefs transportation newsletter. "But I think these are not insoluble problems. These are technical problems highway engineers cope with day in day out."

Gary Groat, director of project development for Fluor, said that the company prefers its proposal but that "we didn't see any fatal flaws in any suggestions made. We feel comfortable looking at all the different options."

The concept also must clear a standard federal environmental review before construction begins.

HOT lane opponents say the tolls amount to double taxation because public funds are used to build roads. "We pay the taxes for them; we shouldn't have to pay for them again with tolls," said Jim Wamsley, transportation chairman of the Sierra Club's Virginia chapter. Wamsley said he objected to the Beltway HOT lanes having tolls at all hours, rather than just during peak times.

Others worry that demand will not meet projections after a study by the Metropolitan Washington Council of Governments found that many drivers on that part of the Beltway take short trips.

Shucet said the HOT lane proposal is a chance to get a corporation to pay for something that is sorely needed.

"In spite of all the complexities some folks talk about, it is so painfully simple to me," Shucet said. "There is a road that has room for a certain amount of cars on it. There seem to be more cars and trucks on it than there is room for, and somebody is willing to provide more room."

Tolls on Beltway HOT lanes would go up as traffic congestion increased.