Waypoints can be quite simple, like a string of pearls aroung your track, and each car has a destination waypoint - so you'd aim towards it. Then when you reach that waypoint, the car would aim towards the next one until it found the end of the loop and it could go back to wapoint 0. Something like that to start with is a good idea, then you can build on the car AI and expand on the waypoints, maybe to hold the desired car speed too, like on a straight you might have a waypoint at the start, then one before the first corner that would tell the car to slow down. If a car looses track of it's waypoint, you can just aim towards the closest one - also the distance to the next waypoint can be used to ascertain which position the car is in (like going by the waypoint, number of laps completed, then the distance to the next waypoint).
I might be able to knock up an example, not sure when though - working on an advanced terrain road example right now, so it could be bolted onto that afterwards (I already have a waypoint system that's quite straightforward and would be ok for racing games).
Van-B
It's c**p being the only coder in the village.
