PURPOSE: To perform correct control of a system, by using a distance sensor, applied with light, and preventing a mistake in short and long distances.

CONSTITUTION: An output from a distance sensor 1, output from a car speed sensor 7 and output of a wheel direction sensor 8, detecting the direction of a wheel, are input to a microcomputer 2, and whether approximating to an obstacle or not is decided from a relative speed. When approximation to the obstacle is decided by the microcomputer 2, a decision is performed from a car speed and a distance from the obstacle to calculate whether a brake 6 is applied or not, and displays 3, 4 are operated. Further to decrease the car speed, control is performed in such a manner as to, for instance, release an accelerator 9 and apply the brake 6 through a controller 5.