Abstract: A measuring system particularly for measuring the length of a moving vehicle comprises a pair of detector stations spaced a known distance apart along a path of vehicle movement each detector station comprising a vertically extending series of electromagnetic radiation beam-emitters disposed on one side of the path and at least one detector disposed on the other. The beams from the emitters are aimed at the detector so that each part of the vehicle when disposed between the emitters and detector will interrupt some of the beams to produce a characteristic quantity of incident electromagnetic radiation on the detector which will serve to identify that part of the vehicle. Data processing means are provided for processing the outputs from the detectors at the two stations to provide a velocity related vehicle measurements.