The idea intrigued Kathy Gillen: Pay highway taxes by the mile instead of the gallon.
So the Otsego, Minn., resident signed on for one of the nation's largest experiments to test how a state might keep track of miles a vehicle is driven.
But the technology wasn't quite up to the task.
"It counted twice a couple of times, and didn't count at all a bunch of times," Gillen recalled.
The recent experiment involving 500 drivers in the region reflects a desire by state officials to find an alternative to the gasoline tax, a highway funding powerhouse that's likely to diminish as cars become more fuel-efficient.
The results, however, suggest that mileage fees face a long, bumpy road to becoming reality.
The smartphone technology installed in the volunteers' cars failed in about a third of the trips. Weak GPS signals caused problems. Double-counted miles were a frequent problem — in one case a vehicle was recorded traveling 57 percent farther than its odometer showed it did.
Only one in five drivers were confident that their fees were accurately tallied.