So, this list differs only slightly from a regular pre-planned camping trip, (or going to visit friends and family), the only difference is the time spent preparing and some of the materials may be more long-term related.
One HUGE difference is the travel times involved. Driving 250 miles under normal circumstances is no problem. Driving that same distance while several million other people are trying to do the same is an absolute nightmare.
You need some safe way to store extra gas and water, not to mention a vehicle in excellent shape. Driving 5mph for ten hours is very hard on a car.
-Blast