A train event recorder – also called On-Train Monitoring Recorder (OTMR), On-Train Data Recorder (OTDR), 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, the performance of the train in response to those controls, and the operation of other train control systems. It is similar to the flight data recorder found on aircraft.
