Electronic braking system

A method of testing the operation of a back-up pressure source in an electronic braking system for wheeled vehicles which has an electronic controller for producing, in response to driver braking demands, electronic signals for controlling the braking pressures applied to the vehicle wheels from a main source of braking pressure, the system having a second, back-up source of braking pressure which can be selected when required, said method comprising:

• generating, in response to said driver braking demands, said electronic signals for controlling the braking pressure applied to the vehicle wheels from said main source of braking pressure;
• establishing whether the vehicle is being braked and has come to rest;
• establishing whether the prevailing driver's braking demand is above a predetermined threshold;
• switching over from said main source of braking pressure to said back-up pressure source at selected occasions when it is has been determined that the vehicle is being braked and has come to rest, provided that the prevailing driver's braking demand is above said predetermined threshold;
• and performing a test on the braking pressures generated by the braking system while it is energized by the back-up source, and generating a warning signal if the back-up source is found to be faulty.