Impact detection sensors are disposed with ease for coping with an oblique collision or the like. A front wheel is disposed between left and right forks and supported by an axle. Main sensors are attached to the left and right forks at respective positions near and above the axle so as to be symmetrical. Thus, the main sensors detect impacts resulting from front and oblique collisions. In addition, backup sub-sensors are attached to the left and right front forks at respective positions above the corresponding main sensors so as to be symmetrical. This makes it possible to dispose the impact detection sensors at sensitive positions with ease while eliminating a steering component.