Hybrid Perks May Become Problems

"The HOV lanes will get clogged up, as they're starting to in Virginia, and they won't any longer serve the purpose of giving people a carpool time advantage," Poole said.

Hybrid buyers enjoy federal and local tax incentives that can offset the extra cost of buying the vehicles, which are generally priced a few thousand dollars higher than other types of cars in their class. Last year, for example, the District passed a law exempting hybrid buyers from its 6 percent excise tax on car purchases.

Spurred by a change in federal law in the fall, five states joined Virginia in allowing hybrids to use carpool lanes, said Christina Rewey of the National Conference of State Legislatures. At least five others, including Maryland, are considering similar measures.

Numerous cities, such as Los Angeles, Albuquerque and New Haven, Conn., allow hybrid owners to park free in metered spots. Baltimore approved a measure in October that allows hybrid owners to pay half-price for parking in certain city garages.

The privileges are being pushed by environmentally conscious politicians and by automobile manufacturers, many of whom trumpet the perks in their sales pitches.

"We'd like to see incentives for all alternative-fueled vehicles as widespread throughout the country as possible," said Eron Shosteck of the Alliance of Automobile Manufacturers, who said the perks are designed to stimulate the market for the cars. "What you're doing is creating a greater incentive for consumers to spend the extra money that these vehicles cost."

Shosteck envisions a separate driving world that includes hybrid-owner-only express lines at motor vehicle department offices and even free carwashes.

Lawmakers behind the measures in Virginia and in other states say their goal is to spur sales of the low-emission, high-gas-mileage vehicles to improve air quality and reduce the nation's oil dependence.

"I know a lot of people put the focus on easing trips on HOV lanes, but my interest has always been in the clean air aspect," said Del. Kenneth R. Plum (D-Fairfax).

Plum, echoing other hybrid supporters, added that if the HOV lanes are clogging, the state should target cheaters, who constitute about 15 percent of users.

Sen. Jeannemarie Devolites Davis (R-Fairfax), who sponsored the Senate bill, added that the HOV incentive gets people out of their gas-guzzlers, not out of carpools. "If they're going to be a single driver, this encourages them to drive a fuel-efficient vehicle," she said.

Hybrids might not serve the purpose of improving the environment while they're cruising the carpool lanes.