PURPOSE: To improve the traveling safety by reducing the engine output when the possibility of the contact with an obstacle is judged from the distance from the obstacle and the relative speed, operating a brake, releasing engine brake when slip is detected and applying brake only by a brake power.

CONSTITUTION: A calculation unit 12 calculates the distance front an obstacle and the relative speed by utilizing laser radar units 122 and 124, and detects the possibility of the contact with an obstacle. When the possibility of contact is judged, an alarm buzzer 134 operates, and a whole control unit operates to apply the engine brake by an engine. Further, a brake is operated by controlling the hydraulic pressure by a brake pressure adjustor 54. In this state, if a slip is detected from the information of the revolution speed sensor of each wheel, slip control is carried out, and engine brake is released, and brake is applied only by the brake power due to the brake pressure adjusting mechanism 54.