Old cars and trucks in the Dallas area – many of them little more than smoking beaters – will get a lot more valuable beginning in December.

In an effort to improve air quality in the Dallas-Fort Worth area, the state will offer up to a $3,500 bounty of sorts on vehicles that are more than 10 years old – pre-1996 cars and trucks that emit up to 30 times as much pollution as late-model vehicles.

Owners who agree to "retire" their vehicles will get $3,000 vouchers that can be used toward buying a new car or truck or a late-model used vehicle. If they opt to buy a hybrid, they can get $3,500. The program is strictly voluntary.

"By cleaning up some of the old cars and getting them off the road, you could put a real dent in the pollution numbers," said state Sen. Kip Averitt, R-Waco, who sponsored the "accelerated vehicle-retirement program."

The program already has funds, generated by higher vehicle state-inspection fees in the Dallas and Houston areas.

Environmentalists regularly castigate big late-model SUVs such as the Excursion and the Hummer, but the dirtiest vehicles on the road are pre-1996 cars and trucks. The older cars also tend to be driven by the working poor and others who can't afford a new car or truck.

Starting in 1996, automakers equipped U.S. vehicles with more sophisticated and precise fuel-injection systems, better sensors and improved computers to meet increasingly stringent clean-air standards. In the years since, most vehicles have gotten dramatically cleaner.

Still, any move to take old cars and trucks off the road will be controversial with some enthusiasts who want to protect collectible cars.

"I guess I'm always suspicious of a program like that," said David Graves, president of Dallas Area Classic Chevys. "It's such a broad approach. They have good intentions. But because they don't consider all aspects of the thing, they may take out some valuable vehicles."

While the differences in emissions between old and new vehicles vary based on the pollutant, Mr. Averitt estimates that old cars and trucks emit 20 to 30 times as much pollution as a new vehicle. Jim Marston, regional director of Environmental Defense, said a more realistic number is about 10 times as much pollution.

Whatever the amount, the plan to get old vehicles off the road makes sense, Mr. Marston said.

"Vehicles after 2002 are markedly cleaner than older cars," he said.

A vehicle-replacement fund was established for this area six years ago, but it only offered $1,000 in assistance and attracted few participants. The Legislature "put the program on steroids" this spring, tripling the amount available to low-income drivers, Mr. Averitt said.

"The old bill just didn't have juice. It was ineffective. We restructured the program to make it available to a wider population and to make it more enticing. EPA deadlines are looming, and we want to make our program as effective as we can," he said.

The old program was so low-profile that it had accumulated about $100 million in unspent funds. That money will be made available to the new program, so there won't be an increase in vehicle-inspection or title-transfer fees, Mr. Averitt said.

"That should be enough to do 40,000 or 50,000 cars [in the Dallas and Houston areas] over the next two years," he said. "It's kind of a gamble because it has never worked here. But I'm confident we can do $100 million and show the federal government and the EPA that we're very serious about attacking our air pollution problems."

The Dallas, Houston and Beaumont areas still don't meet federal clean-air standards.

That means residents pay a $39.75 fee for an annual inspection of a car or truck while people in areas that meet clean-air standards pay $12.50. Some of the additional revenue goes to the car-replacement program.

If half of the 40,000 vehicles come from the Dallas area, it could have a fairly substantial impact on air quality.

"Let's say emission amounts for old vehicles are 10 times as high as new vehicles," said Mr. Marston of Environmental Defense. "You multiply that 40,000 by 10 times and that starts to be a real number. In Dallas, that would be equivalent to about 10 percent of the vehicles on the road."

That alone is not enough to bring Dallas into compliance, but every step counts.

"There is no magic solution to the problem," Mr. Marston said. "The way you solve it is like eating a hippo sandwich – one bite at a time."

The U.S. Environmental Protection Agency had no specific comment on the Texas program, nor did it have data comparing new-car emissions with those of old vehicles.

"The accelerated [vehicle retirement] program is one of many viable options that states can take to improve their air quality," EPA spokeswoman Enesta Jones said. "EPA supports any efforts to improve air quality."

Operational details of the Texas program are still being developed, Mr. Averitt said. The North Central Texas Council of Governments will administer the program, and the rules should be formulated by the end of the year. But the bill's general provisions are:

•Vehicles must have passed a state inspection within the last 15 months, and their owners' annual income cannot exceed $61,000.

•For cars that qualify, a $3,000 voucher will be issued that can be used as a down payment on a new vehicle. The new vehicle cannot cost more than $25,000. The voucher can also be applied to used vehicles that are no more than 3 model years old.

•Participants can use their $3,000 vouchers on new light-duty pickup trucks and some SUVs, as well as used trucks up to 2 model years old.

•People who want to buy a hybrid can qualify for $3,500 vouchers for a new vehicle or a hybrid that is no more than 1 year old.

Texas dealers may benefit from the changes, but they didn't lobby for them. In fact, many of them don't even know about the program yet.

Mr. Averitt said he came up with the idea when he realized that the existing plan was not effective. He later approached some car dealers and manufacturers because the program needed a way to dispose of the salvaged cars.

The car dealers and manufacturers' cooperation is crucial because only 10 percent of the program funds can be used for administration, Mr. Averitt said, leaving it with little money for advertising.

"It's obviously in their interest to participate," he said. "I've visited with Ford, GM and Chrysler. They have ongoing marketing efforts, and it wouldn't cost a dime to include a mention in their marketing of this program."

Dealers must take the old cars and trucks traded to them and turn them over to salvage operations. The salvagers will get the vehicles for free and are supposed to recycle everything but the engines.

With a $25,000 cap, new-vehicle purchases will likely be limited to compact cars, midsize sedans, midsize SUVs and low-end full-size pickups – cars and trucks that don't generate a lot of profit, noted Drew Campbell, president of the New Car Dealers Association of Metropolitan Dallas.

"Is it going to move the dime on the overall market here? No," he said. "But if you think about how many cars we sell in a month in this market – and if this area ends up with most of the sales – you're adding a month's worth of sales."

That's fairly significant for dealers, Mr. Campbell said, and it should certainly have some impact on overall air quality.

"If the fleet turns over, the air gets cleaner," he said. "It's not a broad, sweeping fix, but a piece of the mosaic that leads to a fix."

Details are still up in the air, but the salvage program is expected to work like this:

• Your four-door 1990 Ford Taurus GL wagon has 150,000 miles on it and still runs. According to Kelley Blue Book, the car has a value of $475. Take it to a generous car dealer who really wants your business and you might get $1,000 for it.

• After December, you should be able to take the car to a state office to be inspected. It needs to have passed a state vehicle inspection within the last 15 months.

• If you meet income guidelines, you'll get a voucher for $3,000 to use as a down payment on a late-model used car or most new cars or light-duty trucks priced up to $25,000.

• If you buy a hybrid, the voucher amount increases to $3,500.