Idling a heavy truck engine to keep a driver cool while sleeping at a rest stop is a common but wasteful practice. The use of a new technology to store “cool” from the existing air conditioning system while the vehicle is on the highway can eliminate the necessity of idling to maintain the driver's comfort over a summer rest period.Clathrate hydrates are employed in an economical and effective system for cool storage. An introduction to the application of clathrates for thermal storage is presented. System considerations for truck sleeper application are discussed together with basic system economics. Cool storage equipped vehicles are operating in the field in over twenty five major fleets and idling, to provide air conditioning for resting drivers, has been eliminated. Typical performance for a unit in one of these vehicles is reported.