[Piwoslaw]

I admit that with a GPS in a car it is theorically possible to know one's exact location, which is on the invigilation side. But could a GPS device be constructed in such a way that it only records the distances on certain roads, and maybe whether the speed limit was exceeded, but not the car's exact position? This wouldn't be invigilation, it would only be enforcing the law: speed limits and use of roads.

On the other hand, today's GPS units are still inaccurate: Imagine you are on a dirt road going parallel to a highway. The device may think you are within the position tolerance of the more expensive road and charge you for that. Also, you can hide in a tunnel, underground parking, etc.