The nearest garages are often far away causing towing prices to be rather large. Good planning is crucial. If a failure occurs on a trip, most seem to happen on the highway heading toward the trip's destination. They are usually the normal things like overheated radiators, leaking hoses and broken fan belts. On occasion off road travel causes failures as well.
Punctured tires seem to be typical failures here.
A cellular phone or CB radio would be a great idea in case of mishap. Some travel areas are devoid of service stations. Gasoline and it's usage becomes an important item. My favorite example of this is Mitchell Caverns in the Mojave desert. Careful scrutiny of mileage and gasoline consumption is necessary to avoid running out when traveling in that area.