PURPOSE: To prevent a pedestrain-catching accident by actuating a side object detecting means installed on left side of a vehicle which interlocks with the operation of steering with steering wheel on the right side at leftward front or rightward back movement.

CONSTITUTION: Switches 11a, 11b closing only when a car comes in contact with an obstacle are provided in a circuit conducting on turning a winker switch 16 to "left turn" position, and a circuit configuration is such that a relay 21 is conducting when the switches 11a, 11b are closed, and contacts 21, 21b are closed to a buzzer 20 blowing. Further an arrangement is such that when the car is steered backward, a switch 18 is closed, a relay 17 is actuated to close a contact 17 and open a contact 17b, and the alarm 20 is actuated in the same operation as descrived when the winker is turned to "right turn".