One of California's most coveted motoring perks is up for grabs again.

The yellow decals that give nearly 85,000 solo drivers of fuel-sipping hybrids – mainly Toyota Priuses – free access to the state's carpool lanes are set to expire at the end of 2010.

Now, some lawmakers want the state to give out another round of the stickers in January 2011 to boost sales of the next generation of super-efficient vehicles.

But the move has automakers feuding over exactly which cars will qualify for the stickers, which can boost a vehicle's value by thousands of dollars. It could draw scrutiny from federal highway officials, who have already ordered the state to clear up congestion in overcrowded carpool lanes. Transit advocates argue the state should use the lanes as intended, for carpools and buses.

For General Motors, which is sponsoring a bill to issue 65,000 new carpool stickers for vehicles getting better than 65 mpg, a flood of new decals in early 2011 would coincide nicely with the launch of its Chevrolet Volt. The company promises the car, the first mass market plug-in hybrid, will run 40 miles on a battery charged from a wall socket. A gasoline engine will kick in for longer trips.

The Volt is likely to cost more than similar standard hybrids and consumers may be leery of its new technology. GM hopes to hook buyers with carpool-lane access.

"It's just a very, very important public policy tool that we think will help us make this … viable," said GM spokesman Dave Barthmuss. Plug-in hybrids will qualify for a $7,500 federal tax credit as well as state incentives. GM is also seeking other breaks for the Volt, from bridge-toll exemptions to free parking.

Toyota and Ford have lobbied for changes in the GM-backed proposal, Senate Bill 535. Their opposition helped to stall it this year. Hearings on the issue are likely to be held in the Senate this fall.

Toyota and Ford objected to the 65 mpg standard in part because it would probably exclude their models, at least at first. Toyota also argued that using a miles-per-gallon standard was inappropriate because the federal government hasn't finalized a method for measuring the fuel efficiency of plug-in hybrids.

In the next few months, Toyota plans to launch a 500-vehicle test of its plug-in hybrid, capable of running 12 miles on battery power. But the company isn't expected to roll out the technology widely until after the Volt's release. Ford plans to market a plug-in hybrid by 2012.

Curt Magleby, Ford's director of state government affairs, said his company would prefer that a wider variety of models – including vehicles that make fuel-efficiency improvements within a class, such as hybrid SUVs – be eligible for at least some stickers.

Electric-vehicle advocates say GM is taking a risk with the Volt, and other carmakers ought to do the same if they want to qualify for the stickers.

"Toyota is really resting on its laurels," said Jay Friedland, legislative director for Plug In America.

Mainstream environmental groups have been pointedly neutral. While they don't want to be seen as hindering sales of fuel-efficient vehicles, they worry that hybrids clog carpool lanes. On balance, staff members at several groups said, it's not clear that issuing more stickers would deliver an environmental benefit.

Some public transit advocates, though, are strongly opposed to the bill. Stuart Cohen, executive director of the statewide group TransForm, said some of the Bay Area's most congested carpool lanes – in southern Marin County, Palo Alto and Berkeley, for instance – are also places where residents need little extra incentive to invest in a green car.

"These are the people that are going to buy these things anyway," Cohen said.

The hybrid sticker program was created by a 2004 state law. Cohen fought that measure too, as did Ford, which argued that it would subsidize Japanese hybrids to the detriment of American models.

Earlier, a 1999 law had authorized issuing carpool stickers to cars running on natural gas or full battery power. But only about 9,500 vehicles with those stickers – which are white instead of yellow – are in use, according to the Department of Motor Vehicles.

These white stickers are set to expire at the end of 2010, but would be renewed under SB 535. Their usage is likely to go up, as a number of all-electric vehicles are headed to the market, including a mass-produced model from Nissan.

The yellow stickers were an instant hit, with nearly 40,000 snapped up in the first four months they were available. A 2006 bill raised the cap on the stickers from 75,000 to 85,000, and extended by three years their original sunset date.

The sets of four stickers, issued by the DMV for $8, were to be stuck on the vehicle they were assigned to and stay with it, even if it's sold (though it's not hard to find offers online for unused stickers).

Since the state hasn't issued any new stickers since 2007, they've grown precious. A used car with stickers is worth more than a similar one without. In 2007, a Kelley Blue Book survey for USA Today put the premium at $4,000.

Legislators have several times proposed expanding carpool-lane access. One bill proposed this year would give stickers to doctors responding to an emergency. Another would add veterans and active-duty military personnel. Both are still in committee.

California is one of eight states to give hybrids access to carpool lanes. The state had to get permission from the Federal Highway Administration, which has expressed concern that the state is overloading the lanes. Under federal orders, Caltrans officials are developing ways to unclog the lanes, such as with electronic signs that would order hybrids out of the carpool lanes when traffic speeds drop below a certain level.

Call The Bee's Jim Downing, (916) 321-1065.