I’ve never found it to be a problem even in a giant, armored RV.
Just go slow when you hit the spots that are thick with dead cars and slowly weave between them.
Oh, and make sure your driving skill is four or higher so that you won’t randomly ram into the other cars.
Also am I the only one who thinks that Cataclysm people with drive skills below four act like they’ve got some sort of suicidal palsy the moment they get behind the wheel? Every ten seconds they’re grabbing the wheel and cranking it, trying to kill themselves on the nearest obstacle for no particular reason. I don’t think I could drive that badly IRL if I was blind drunk.