why do you need GPS to track mileage? (Score 1)

If the whole point is to track the mileage that people use and levy the taxes based on the mileage one drives, you don't need GPS to do so... everyone has to have a registration, an inspection sticker, etc... So why not get the mileage from the car when you renew it? I'm sure there are a small (relatively of course) number of people that drive interstate often and would not have their mileage correctly applied to the correct state, but it should even it self out... To me this sounds like a really bad idea under the guise of "fairness"...