It is an object of the present invention to provide a technique to increase efficiency of the output torque of the blushless motor to drive a power tool. The travel controlling apparatus is provided with a roadside zone distance measuring device for measuring a distance from the vehicle to a roadside zone provided in a side of the traveling path, and the present position and azimuth is determined on the basis of the roadside zone distance measured by the roadside zone distance measuring device. Each of the parallel side walls comprises an outer side wall portion and an inner side wall portion.