Hybrid drivers could begin using the lanes within weeks.

The policy change was designed to encourage drivers to buy the high-mileage, low-emission vehicles. But the announcement that hybrid drivers can apply immediately for the decals came as a surprise to backers of the change, who had predicted that it might not be implemented for months.

California's law was supposed to take effect Jan. 1 but first needed approval from the federal government. That permission was tucked into the transportation bill.

The state originally planned to wait for clean air regulators to reconcile the state bill with the federal legislation, which supporters had said could take months. But the state Air Resources Board had time to review the state and federal legislation before Bush's signature, and decided to proceed with the change immediately, said Gennet Paauwe, a spokeswoman for the board.

Gov. Arnold Schwarzenegger said in a statement that the change was "a common-sense policy" toward reducing air pollution. The state has some of the most polluted regions in the nation.

"The more we can encourage Californians to buy and drive cleaner-air hybrid cars and trucks, and give them some incentive to do so, the better off we will all be," Schwarzenegger said.

Reps. Brad Sherman, D-Sherman Oaks, and Darrell Issa, R-Vista, pushed to include language in the highway bill allowing California's law to take effect.

"It's good news for really everyone in the country and the world that wants to see us switch to a cleaner, more fuel-efficient technology," Sherman said.

Only three hybrid models _ Toyota's Prius and Honda's hybrid Civic and Insight _ will be allowed in the lanes. They are the only models that meet the eligibility standards of at least 45 miles per gallon and almost no smog-causing emissions, according to the office of the bill's author, Assemblywoman Fran Pavley, D-Agoura Hills.

Hybrid owners will have to send in applications and $8 fees to the Department of Motor Vehicles to receive their decals.

Cathy Margolin, president of the Orange County Prius Club, said using the car pool lanes will shave an hour each day from her commute between Newport Beach and Fullerton.

"It's an incentive for drivers to switch to hybrids instead of driving their gas guzzler SUVs," she said.

Hybrids get better mileage by supplementing gas with electricity harnessed from the engine during braking and coasting.

California will become the second state to allow hybrids with solo drivers to use car pool lanes. Virginia enacted the change in 2000, and Arizona, Connecticut, Georgia and Minnesota are considering it.

Some Virginia drivers complain that allowing hybrids in the lanes has led to a crush of cars and slowed once-speedy commutes. The American Lung Association of California advocates hybrids but took no stand on Pavley's bill for fear it might cut car pooling and lead to more pollution.

To prevent hybrids from clogging the lanes, Pavley's bill expires in 2007 and caps at 75,000 the number of hybrid vehicles that could participate.

As of the end of June, there were 57,164 hybrids registered in California, though not all would be car pool-eligible, according to the Department of Motor Vehicles.

In a sign of the vehicles' growing popularity, nearly 24,000 hybrids were registered in the first six months of this year.

To qualify for the stickers, motorists in the San Francisco Bay Area will also have to have a FasTrak pass and transponder that allow them to drive by toll bridge booths without paying. Stopping at a toll booth would add to air pollution, state officials said.

Hybrid owners can get an application for the permits from the DMV Web site or from a DMV office.