Also, if you're gonna have vehicles, you need to have fuel. I can't remember at the moment what they run on in the Fallout universe, but again... Depending on how much time has passed since the bombs fell, it would seem that most sources of fuel would've likely been scavenged long ago. That was one thing I didn't like in Fallout 3, how much stuff there was just lying in the gameworld even with all the time passed.
In Fallout 2, the car runs on small energy cells and microfusion cells, just like all energy weapons.
I just hope they don't copy paste the various factions from Fallout 1 and 2 (Super Mutants, Enclave, BOS, etc) like Fallout 3 (wasn't that bad to me but still). That's why I hope Caesar's Legion and other new groups show up. I also think if they didn't include a vehicle they should make a fast travel system like Fallout 1/2.
Well, in FNV the old factions appearing makes more sense than in FO3, given how close New Vegas is to locations from the original games.