Abstract: An apparatus for measuring side-to-side tilt of vehicles such as trucks, trailers and the like that elevate one end of a bin to dump material therefrom. A curved transparent tube filled with liquid except for one gas bubble is mounted on the vehicle. A series of light emitters are arranged along one side of the tube with a corresponding series of light detectors along the other side. The detectors detect light passing through the liquid but not through the bubble. The resulting signals are transmitted to at least one light bar having a series of light emitters, such as incandescent lamps or light emitting diodes. An electronic circuit processes the tube detector signals and causes the light bar to light emitters in a pattern corresponding to the degree of tilt. An audible alarm and a circuit for stopping bin lifting when tilt reaches a predetermined limit are provided.