A mobile tracking unit capable of operating in a power-starved environment for a vehicle tracking system includes a navigation set for generating data corresponding to a respective vehicle position. The navigation set is periodically energized at a selected activation rate F.sub.G while the vehicle is moving to generate the vehicle position data. The tracking unit includes an electromagnetic emitter which is capable of transmitting the vehicle position data and which is periodically energized at a selected activation rate F.sub.EM while the vehicle is moving to transmit at least the vehicle position data. A motion sensor is employed for generating data indicative of vehicle motion. A tracking unit controller receives the vehicle motion data and controls the navigation set and the emitter based upon the vehicle motion data so that when the vehicle is stationary each of activation rates F.sub.G and F.sub.EM can be respectively decreased by a predetermined factor, thus reducing the overall power consumption of the tracking unit. The tracking unit controller is further designed to return to activation rates F.sub.G and F.sub.EM upon the motion sensor sensing renewed vehicle motion, thus avoiding loss of vehicle position data during times of renewed vehicle motion.