Abstract: Apparatus is provided for determining the relationship between a vehicle's thrust line and the vehicle's body center line. A movable light source is located externally of and independent of the vehicle and serves to establish a pair of reference light beams falling in parallel planes and which are spaced apart sufficient to permit a vehicle to be positioned longitudinally therebetween. The vehicle's thrust direction is determined by mounting sensors on the nonsteerable wheels so as to extend transversely away from the vehicle's body to intercept the light beams, together with circuitry for providing output indications dependent upon the location of light interception and which indications are representative of the vehicle thrust direction. The body center line is determined by employing targets which are mounted to body sides of the vehicle to intercept reference light beams.