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 other incidents, but is also used to monitor the performance of traction units, the competence of drivers, and the general state of a train over a period of time.

[1] In 1864, a similar proposal came from Charles Babbage, inspired by his 1840 experiments for the Great Western Railway using self-inking pens on paper rolls, which were part of the equipment carried on dynamometer cars.

[citation needed] The need for event recorders to survive any accident led companies such as Grinsty Rail (UK), Faiveley (France), Hasler Rail (Switzerland), Bach-Simpson (Canada), Saira Electronics (Italy) (previously FAR Systems), and MIOS Elettronica (Italy) to develop crash-protected memory modules as a part of their event recorders.

[7][failed verification] Canadian regulations provide in the "Locomotives Design Requirements (Part II)" U.S. regulations define event recorders as follows: (CFR 49 Ch II 229.5): The Federal Railroad Administrations (FRA) "Final Rule 49 CFR Part 229", (revised June 30, 2005)[10][11] requires that event recorders be fitted to the leading locomotives of all US, Canadian and Mexican trains operating above 30 miles per hour (48 km/h) on the US rail network including all freight, passenger and commuter rail locomotives but does not apply to transit running on its own dedicated tracks.