Fact: Revenues from gasoline taxes are failing to keep pace with the need for money to finance transportation projects. That's because the taxes are pegged to the amount of gas sold, and volumes are leveling off as people switch to vehicles that get better gas mileage. Having to pay in the $4 per gallon range will do that to you.

Well, if Plan A no longer is getting the job done, what about Plan B? The problem is that Plan B understandably gives many people the willies.

It hinges on tracking the number of miles driven instead of gallons used -- along with where those miles are driven, so that taxes could be allocated to the appropriate states. Some sort of tracking technology would have to be used.

Not that the vast majority of us have anything to hide, but there has to be a fair way to collect adequate revenues to build and fix roads that doesn't potentially amount to filing a record of each and every trip with the government.

As The N&O's Bruce Siceloff reports, an experiment with this sort of system is getting under way in the Triangle as part of a six-state test. Volunteers will have their trips tracked by a GPS device.

The data will be converted into make-believe gas tax bills, with rates adjusted downward for more fuel-efficient cars. Money would be payable to states where the driving occurred.

Now, someone driving a hybrid will pay less in gas tax than someone driving a gas guzzler the same number of miles. That poses a revenue problem as gas guzzlers go out of style. But it's hard to see how the new proposal could raise much more money without also amounting to a tax increase. Why not just raise the current gas tax? Factoring in a potential invasion of privacy, the mileage tax plan doesn't look ready for prime time.

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