Self testing process for a railway brake system

A brake system has a brake ECU comprising a microcontroller and a non-volatile memory. The non-volatile memory is adapted to store the result of tests on the safety circuits carried out during, before or after operation of the brake system, the result of the tests being assigned one of at least two statuses, at least one of the said statuses being indicative of an unhealthy test. At start-up of the brake system self-tests are carried out on the circuits or components of the brake system for which an unhealthy status has been stored in the non-volatile memory, thereby enabling the brake system to operate prime functions without prior self-test. The tests may be performed at closedown and prioritised, with failed tests the highest priority and overdue tests the next priority.