Hmm, let me think about this for a second.
I live in suburban New Jersey. My current vehicle is a 2004 Honda Accord V-6. It has traction control and a GPS system, so if I have to go out into
the wilderness of Warren County*, I won't get lost. Off-roading probably won't be of much use, since most of the terrain around here is either
homes, strip malls or dense forest that either any vehicle can get through, or no vehicle can get through.
In a SitX scenario, I guess the only sane thing to do would be to just hang myself and spare myself the misery -- check
this link to see why. (And maybe I'll... get myself off in the process, I hear it feels
awesome.) But that's no fun, is it?
I'd discount any large 4x4, as it would first have to get past lots of traffic on clogged highways, and then it would burn through fuel like Charlie
Sheen burns through drugs. This is where a smaller sedan with traction control has the big 4x4s beat -- in fuel economy and maneuverability. To see
what I'm getting at, try parking a regular car, and then try parking one of those big, "survival-ready" 4x4s. Now imagine trying to do that all the
time on a crowded road, where the cars aren't "parked" quite as neatly, without damaging your vehicle. If you live within 100 miles of a major
city, you'll get a lot farther in a little Accord than you will in that big Unimog. (Even better would be a motorcycle, assuming you know how to ride
one and aren't injured.) Remember -- the old "grand tourer" automobiles, designed for long-distance road trips and endurance driving, were not
off-road vehicles, but were compact sports cars. And even after SitX, usable roads (even dirt ones) will persist long after the last working
automobiles have been locked away by the post-apocalyptic warlords for their personal collections.
Which brings me to the next section -- what happens when the gas runs out and you can no longer run your car, truck, motorcycle, ATV, etc. A lot of
you guys have recommended horses. A century or two ago, this may have been the case -- indeed, it would've been the default option. However, from
what I've seen in this area (i.e. at county fairs, racetracks and the like -- it may be different in other parts), most horses now are bred not for
endurance, but for racing and beauty. Worse, many of them are purebreds, which means that you get all of the incest-related genetic illnesses that
come from breeding animals for specific traits. Also, while wild horses may be able to persist on grazing alone, work horses can't -- they need shoes
(which break), medicine (which will be in short supply), and feed to sustain them for the work that they do (grazing alone just won't cut it). And
the modern breeds of horse that we have are not naturally-occurring, but rather, they are all domesticated forms of ancient horses that are much
smaller -- so-called "wild" horses may be more properly called feral horses. And what happens if your horse gets scared or irritated? I'd ask
Christopher Reeve, but he's been dead for a while now. In short, maintaining a horse is a far greater task than most people think.
So instead of a horse, I'd go with a bicycle. No gas or feed, easier to maintain (although you need tools), and more maneuverable. Sure, if you get a
flat you're screwed, but then again, you're screwed if your horse splits its hoof. Ultimately, the final option for transportation is to travel on
foot.
So, after SitX, I'll start with my car, then go to my bike when that runs out of gas or breaks down, and start walking when I can't use that
anymore.
* Heh. What does it say about me that I consider Warren County, New Jersey, population >100,000, to be the wilderness?