On Train Monitor Recorder (OTMR) or On Train Data Recorder (OTDR)
OTMR is essentially an airline style “Black Box Data Recorder”. In common with the airlines, the black boxes are actually painted Orange.
The Railway Safety and Standards Board (the RSSB) issue a large number of Railway Industry Standards (RIS documents) and one of these details the information that shall be recorded on the OTMR. This includes the speed, several inputs from the automatic brake system, inputs from the TPWS/AWS system, the use of the warning horn, power handle position, to name but a few.
The OTMR equipment is produced by a small number of approved suppliers, as the equipment must be proven to be robust and reliable enough to be used as evidence in a court of law in the event of a criminal case arising from an operating incident.
Whilst it has an overtone of Big Brother, it is an extremely useful tool for maintenance, for reviewing operational performance and for debates with other rail users over who may have done what at certain times. All operators agree that they would rather be with it than without it these days.