A proposal to extend car pool lanes on Shirley Highway for 19 miles south from the Capital Beltway to Quantico is stirring enthusiasm, anger and no small amount of debate among Northern Virginia commuters and politicians.

In public hearings last night and Tuesday, officials from the Virginia Department of Transportation described plans to widen the highway so that it could accommodate two reversible lanes down the median strip. The express lanes would connect with those that already run down the center of Shirley Highway (I-395 and I-95) from the Potomac River past the Beltway.

The $200 million project was supposed to begin next fall but has been postponed for at least two years because of a loss of federal highway funds, officials said.

Supporters say the extension of the car pool lanes is made necessary by the increasing numbers of Washington-bound commuters from Prince William County and the Fredericksburg area.

"It's the most effective transportation mechanism in Northern Virginia," said Fairfax County Board Chairman John F. Herrity.

"The current HOV {high-occupancy vehicle} lanes carry three times more people than the conventional lanes."

Others were more critical, contending that car pool lanes are underused and that restrictions should be relaxed.

"It has become apparent that HOV restrictions create nearly as many problems as they solve," said Norma Pandazides, a candidate for Prince William County supervisor from Dumfries who spoke at last night's meeting.

Several commuters objected to the rule that limits express lanes to cars with at least four occupants during rush hour.

David Grant, a Prince William resident who commutes to Crystal City, asked transportation officials to consider the plight of car pool drivers who might have difficulty filling a car when riders are on vacation. "HOV-3 would be great," he said. "If it could be reduced to HOV-2, that would be great."

Building the new lanes would be a major undertaking. In addition to the lanes, the project would involve construction of several new interchanges, including a new loop at the Beltway. The lanes would tie in with the planned Springfield Bypass and provide access to the planned Springfield Metro station.

Transportation planners contend that express lanes are the most efficient way to move large numbers of people on existing highways. During the morning rush hour, more than 31,000 people use the car pool lanes on Shirley Highway, according to the Department of Transportation figures.

At Tuesday's hearing, residents of the Loisdale subdivision in Springfield objected to the widening of the highway because, they said, it would destroy a buffer of trees that separates their neighborhood from the traffic.