According to an article on Wired, Oregon is looking to replace the fuel tax with a tax based on the actual mileage driven by users.

I'm sure that the SUV lobby likes this idea, but privacy advocates are up in arms.

The process involves using a GPS device in each car to track where each individual drives. When you go to the gas station, the device communicates wirelessly with the pump and adds the mileage-based tax on to the gas bill. Privacy advocates don't like this idea.

This tax will replace the per-gallon gas tax. Environmentalists are unhappy with this as it removes the incentive for drivers to use cares with more fuel- efficient engines.