SALEM -- Drive less. Save money. It's a simple concept that one day could change how motorists pay for car insurance.

Supporters, who say such plans can reduce premiums, control congestion and cut pollution, hope lawmakers will help jump-start the idea in Oregon. House Bill 3871 would give companies tax breaks for offering voluntary mileage-based insurance policies.

"To me, it makes sense to try to give people a financial incentive to drive less," said Rep. Charlie Ringo, D-Beaverton, one of the bill's sponsors. "Right now, one of the only direct financial incentives is what you pay for gas. You drive more, you pay more."

The House Transportation Committee unanimously approved the bill Friday and sent it to the House revenue committee. At Friday's hearing, consumer, insurance and environmental groups praised the proposal as an innovative idea worth advancing.

But they also acknowledge that legislators, increasingly under time and money constraints, probably are not ready to embrace the idea this session. HB3871 would reduce state revenue, although state economists have not determined by how much. And because the concept remains in its infancy nationwide, the insurance industry is unsure how soon it could develop and implement an effective, cost-efficient program.

Currently, car insurance rates are calculated by a driver's average risk, determined by factors such as age, sex, driving record and vehicle type. Most policies also take into account some mileage, such as the average length of commute. The idea of insurance rates based primarily on the use of a car is to give drivers control over premium costs, rewarding those who spend less time on the road.

Miles or time driven could be tracked through regular odometer readings or by installing high-tech devices, such as satellite global positioning systems.

"Insurance has conventionally not been able to pool all of the risk factors that are really related to whether you're going to be in an accident," said Chris Hagerbaumer, air and transportation program director for the Oregon Environmental Council. "And miles driven is strongly correlated."

Environmental groups such as the OEC are keen on the idea, which they say would extend beyond consumer savings. Fewer cars also means less traffic, fewer accidents, less pollution and less wear and tear on roads.

Studies suggest that mileage- and time-based plans can reduce driving by 10 percent to 20 percent, said Allen Greenberg of the Federal Highway Administration, which is studying the potential benefits of such plans.

The only insurance company that has tried the idea is Ohio-based Progressive Insurance Co., the state's fifth-largest auto insurance firm with about 57,000 Oregon policyholders. In August 1998, Progressive began a pilot program in Houston to test an in-vehicle electronic system that tracked driver mileage, time of day and general driving-area information. It expanded the test to all of Texas a year later.

The company is evaluating the results to decide whether to expand the program, spokeswoman Courtney Neville said. Offering a mileage-based policy did not reduce company costs, she said, but would not reveal further financial details. The program saved participants about 25 percent compared with traditional plans in Houston, she said.

Brian Boe, a lobbyist for the National Association of Independent Insurers, said his group supports the bill. In a competitive car insurance market such as Oregon, offering companies incentives to provide innovative products is good for consumers, he said.

Whether the idea catches on will depend on the evolution of technology, Boe said. Insurance companies say it's still unproven and too expensive for them to offer. And lobbyist Jack Munro, who represents the American Insurance Association, says electronic tracking raises privacy concerns that could affect the future of mileage-based insurance.

Even if the bill falls short this session, supporters say they are encouraged by the committee's unanimous approval. There could be opportunities to pursue the idea outside the Legislature, Hagerbaumer said, such as Progressive's pilot program, which was conducted in conjunction with several federal agencies.

"We're in the initial stages, but interest is peaking," she said. "We're definitely going to push it to other venues. There's a lot of enthusiasm out there from drivers."