What a great idea for your Dad. In addition to the earlier suggestions about carrying some things for tires, I would suggest you think about a recovery strap. I have had one in my vehicle kit for many years now, and although I haven't actually needed to be pulled with it, I have used it to help some folks who had gone slightly offroad. Because the recovery straps are designed to stretch, they actually work with your vehicle to help extricate the stuck one when they contract again. (Just make sure you drape a tarp or some jackets over the strap in case it snaps, the tarp might slow it down before it kills someone.) You have to be very careful that you attach it to a secure point on both vehicles. In my case, I have shackle attachment that fits into the tow hitch receiver on my Envoy.

I used it once to pull a friends car out of a large pile of snow at the end of our business parking lot. Apparently the car was cold, and was trying to make an emergency snow cave <img src="/images/graemlins/grin.gif" alt="" />

Happy New Year!