NORTH COUNTY -- When it comes to paving roads, going green means delivering a quieter ride and a longer-lasting surface.

For those reasons, area cities are increasingly turning to recycled tires when they repair major streets like El Camino Real, Palomar Airport Road and Coast Highway.

"It's a great use of old tires," said Encinitas Councilwoman Maggie Houlihan. "Some people complain that it is more expensive. But the reality is, it wears better. And it's an example of reuse that is superior in terms of quality of life."

The growing green trend is making state environmental officials happy as they grapple with the daunting task of preventing million of tires from winding up in landfills.

With all the driving Californians do, 40 million tires are thrown away every year, according to the California Integrated Waste Management Board. And about three-fourths of those are recycled.

But 10 million tires land in dumps or illegal stockpiles, where they become breeding grounds for disease-carrying mosquitoes and rodents, state officials say. If they catch fire, waste tires send thick clouds of toxic smoke into the air, and the flames are difficult to extinguish.

Then there's the potential for tires to spill toxic runoff into waterways, officials said. The rubber breaks down over time, and bits of it can wash into nearby streams.

That's why the waste management board from time to time awards state grants to communities for paving projects.

Jon Myers, a spokesman for the waste board, said a single-lane mile of pavement can absorb up to 2,000 tires.

Encinitas received such an award two months ago, totaling more than $76,000, a board news release stated.

The grants defray a portion of cities' cost of purchasing a substance called "rubberized asphalt concrete" that mixes bits of shredded tires with asphalt.

Leroy Bodas, Encinitas deputy city engineer, said the cash doesn't come close to covering the entire cost of the material. In his city's case, the $76,000 represented a small percentage of the $3.2 million cost of an Encinitas Boulevard paving project that got under way last week and will lay down rubber between Coast Highway and Willow Spring Drive.

"But every dime is helpful because we never have enough money to overlay streets," Bodas said.

Solana Beach recently laid old tire rubber along Highway 101 between Lomas Santa Fe Drive and the Del Mar city limit, and along Lomas Santa Fe east of Interstate 5, said Dave Roberts, a city councilman.

And the local California Department of Transportation office is preparing to pave the Lomas Santa Fe Drive underpass at I-5 with rubberized asphalt, as part of a project to reconfigure the interchange, Roberts said.

"It is not cheap, but it is great," he said. "It is environmentally sensitive and it reduces sound. And, of course, the community just loves it. We're big believers in it."

Roberts said Solana Beach officials believe in the tire-cushioned asphalt so much they are lobbying the local California Department of Transportation office to use the material to widen Interstate 5. Caltrans is preparing to extend car-pool lanes on the freeway north to Manchester Avenue.

"As traffic continues to expand on the freeway, it's going to really add to the noise level," Roberts said.

And he said city officials believe that using rubber could turn down the volume.

"As they say, you can't stop progress. And you can't stop I-5," Roberts said. "So you've got to come up with other solutions that are sensible."

However, Caltrans officials aren't sure recycled-tire surfaces make as much sense for high-volume freeways as they do for smaller city streets that see significantly less use.

Edward Cartagena, a Caltrans spokesman, said officials do not believe rubberized asphalt is the best choice for I-5 because it doesn't last as long as the thick concrete Caltrans uses to pave freeways. Cartagena said Caltrans does not have a pot of money sitting around to cover the additional cost.

Caltrans instead is considering a technique called "whisper grinding" to make the concrete on I-5 quieter. And Solana Beach has scheduled a community meeting on the topic for 6 p.m. June 16 at Solana Beach City Hall.

However, Caltrans isn't ignoring the potential that recycled tires offer. Cartagena said the agency is testing the material on sections of Highway 54 in East County and on Highway 75 in Coronado.

When it comes to local streets, the rubber-tire surface is well beyond the testing stage. And communities have discovered recycled pavement lasts longer than traditional asphalt, said Carlsbad Deputy City Engineer Bill Plummer.

The typical pavement on a busy street breaks down after seven years, Plummer said, while rubberized asphalt stays intact for 10.

Besides the Encinitas Boulevard project that is under way, Bodas said his city paved a half-mile of Leucadia Boulevard, between I-5 and Vulcan Avenue, a couple of months ago.

Over the past several years, he said, Encinitas street workers have put the tire-modified pavement down on Coast Highway between Encinitas Boulevard and the Solana Beach city limit. Bodas said people dining at downtown outdoor eateries have noticed passing cars aren't as noisy.

"You'll notice a big difference if you eat at the 101 Diner," he said.

In Carlsbad, the rubber asphalt has been used on sections of Palomar Airport Road, College Boulevard and El Camino Real, among other streets, Plummer said.

"We are about to do Palomar Airport Road this summer from the intersection with El Camino Real east to the city limits," he said.

Contact staff writer Dave Downey at (760) 745-6611, Ext. 2623, or ddowney@nctimes.com.