Kim and his team at Oregon State University equipped a test car with a global positioning device to keep track of its mileage. Eventually, every car would need one.

"So, if you drive 10 miles you will pay a certain fee which will be, let's say, one tenth of what someone pays if they drive 100 miles," says Kim.

The new tax would be charged each time you fill up. A computer inside the gas pump would communicate with your car's odometer to calculate how much you owe.