This paper describes a system designed to assist drivers when backing out of a parking space. The system has the following functions that help to prevent the host vehicle from coming too close to objects behind it or to vehicles approaching it from the rear or either side when reversing. Audible and visual warning advises the driver of the presence of an approaching object. The system generates force to push back the accelerator pedal if it is being depressed by the driver. The system applies brake if it judges that braking is needed. Radar sensors and sonar sensors are fitted to the rear for detecting objects behind the vehicle. A brake actuator and an accelerator pedal actuator for generating force to push back the pedal are provided. A prototype test vehicle was built and driving tests were conducted by a panel of ordinary drivers in public parking lots. The results confirmed that the system worked as designed.