It's a looming problem as hybrids become more popular, and Gov. Arnold Schwarzenegger's government-reform commission has come up with a solution: Tax motorists based on the miles they drive, not the amount of gas they consume.

The idea from the California Performance Review is just that at this point: an idea. It would have to go through extensive debate to come to fruition.

But it's not at all far-fetched. Oregon will do a test run of such a "vehicle- miles traveled" system next year.

The plan, which still requires legislative approval there, would put a $100 global- positioning-system device in every new car in Oregon. The device would beam drivers' in-state mileage to a satellite, which would then send the information to the service station where the driver is refueling so the proper tax can be levied at the pump.

Three hundred drivers will be monitored for six months next year in the Eugene area in the pilot project. The U.S. Department of Transportation, Utah, New York and now California are closely watching for the results.