Abstract: Apparatus and technique for use on a moving rail vehicle to detect, measure and record rail surface and side discontinuity by means of sensors mounted at intervals on the rail vehicle undercarriage. The sensors may be of the contact or non-contact variety, continually sensing track conditions. The sensor signals are transmitted to a peak detection system which evaluates the signals against prior values standarized for optimum track conditions. The system further determines peak values to indicate rail discontinuities. Analyzing, recording, and storing the signals are done with the aid of a computer processing unit and a magnetic tape unit as the storage medium.