The single best thing to do for parked cars, SUV's, motorhomes, trailer homes, airplanes and any movable vehicle that has a rodent issue is to place bait stations such as the Rodent Cafe around the base of the vehicle, under tires, etc. use rodent bait such as Contrac or Ditrex inside the stations, and keep the stations full of bait and inspected at least 1 time per week during the heaviest periods of activity. Traps such as the T-Rex can be placed under hoods, in hidden compartments, even on floor boards to trap them. A hot pepper repellent such as Detour can be placed and smeared onto electrical wires and other areas. This product is very hot and works as a training tool to help stop them from chewing on wires, etc.
Rodent repellent granules such as ShakeAway - http://www.epestsupply.com/cgi-bin/sh...
placed around tires can also be helpful.
Glue traps can also work but not as effectively. The most important thing to remember when developing a plan for rodents that get inside of vehicles is that you have to keep them out if possible. Diligence and a plan that involves daily or at the minimum weekly inspections during the heaviest periods of activity are usually required.