the best police chase ever filmed was "Vanishing Point" the original with Barry Newman, best police chase movie ever in my opinion.
Best car chase movie however not involving police is "Duel" directed by believe it or not Stephen Spielberg and starring Dennis Weaver being chased in an old Plymouth Valiant by this scary old semi. If you can get your hands on a copy of it, it will knock your socks off, even though it was originally a made for TV movie and his student project. It is not easy to find a copy of. You can see a ton of his cool camera work being born in that film.
wiki for duel: pretty cool stuff
http://en.wikipedia.org/wiki/Duel_(film))