Event recorder

A train event recorder (also called On-Train Monitoring Recorder [OTMR] or On-Train Data Recorder [OTDR] in the United Kingdom, Event Recorder System [ERS], Event Recorder Unit [ERU], or simply Event Recorder [ER]) is a device that records data about the operation of train controls and performance in response to those controls and other train control systems. It is similar to the flight data recorder found on aircraft.

Because event recorders are integrated with most car-borne systems, they are an attractive target for enhanced diagnostic and control functions. Some event recorders feature outputs controlling penalty brake or emergency brake (train) systems, and speedometers.

Data storage can be provided by magnetic tape, battery-backed RAM and, more recently, non-volatile EEPROM or Flash Memory overwritten in a FIFO continuous loop. The data is intended for use in the investigation of accidents and incidents but is also used to monitor traction unit performance, the competence of drivers, and general state of the train over a period of time.

A suggestion in The Times of 10 October 1853, commenting on a rail collision near Portarlington station, Great Southern and Western Railway, on 5 October that year, called for a paper-roll recorder to be carried in a locked box on trains, recording wheel revolutions against time, the record to be removed and stored by station masters at the destination station. A similar proposal came from Charles Babbage, arising from his work for the Great Western Railway on dynamometer cars, in 1864. No action seems to have been taken in either case. The earliest event recorders were the mechanical "TEL" speed recorders of 1891, which recorded both time and speed. The TEL's manufacturer, Hasler Rail of Switzerland, remains a leading producer of train event recorders.

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