Which, to be fair, is pretty much The Road's plot synopsis.
Whether they're trying to reach some sort of fabled vestige of civilization, looking for resources or simply trying not to be eaten by zombies, the survivors are always moving from point A to point B, and that means either walking over insane stretches of possibly radioactive desolation or fighting other people for gas. That's just the way it is, though, because if the whole world has gone to s**t, how else are you gonna get around?
So What's Missing?
How about grabbing a bike? In most of these films, there always seems to be a gap between having a vehicle and gas and being s**t out of luck, as if no other possibility existed.