Abstract: A refrigerated semitrailer truck for both long and local delivery of frozen foods in a hot environment is disclosed which utilizes both a liquid nitrogen unit and a mechanical refrigeration unit with an automatic control system. The system automatically turns the liquid nitrogen off when the temperature is above 30.degree. F., below -10.degree. F., or when an access door to the insulated truck is open. The liquid nitrogen also operates as a standby unit at all temperatures above -10.degree. F. in the event of a malfunction of the mechanical unit.