Abstract: A rear obstacle detection and avoidance system for use on a vehicle comprises a rear obstacle detector that is coupled to the vehicle and measures the distance between the vehicle and an obstacle substantially to the vehicle's rear, a speed sensor that determines vehicle speed, an alert generator that notifies an occupant of the vehicle of a rear obstacle, and a processor that is coupled to the rear obstacle detector, the speed sensor, and the alert generator. The processor causes the generation of a first alert when the vehicle's speed is less than a threshold speed and the distance between the vehicle and an obstacle substantially to the vehicle's rear is less than a first distance determined in accordance with a first function of speed vs. distance.