The present invention relates to an apparatus onboard a vehicle for determining an actual alignment condition of the vehicle's axle during either dynamic or static conditions. Proper axle alignment depends on a perpendicular relationship between the axle and a centerline reference of the vehicle, which positions the wheels and tires parallel to the centerline. The invention, being installed onboard a vehicle with axle (58) properly aligned, in one embodiment, readily determines the perpendicular relationship between axle (58) and vehicle centerline (70) by measuring a spatial relationship between at least two control points or benchmarks established on the vehicle. These points may include point (58a) located at axle (58) and point (38) located on the vehicle's body or frame (62). Any change in the spatial relationship between the points is utilized as representation of a change in the perpendicular relationship between axle (58) and vehicle centerline (70).