An apparatus is provided for a vehicle having components of a parking brake system and components of a service brake system. The apparatus comprises a normally-energized solenoid operatively coupled to components of the parking brake system and for, when de-energized, exhausting air pressure in at least some components of the parking brake system to set park brakes. The apparatus further comprises an electronic controller arranged to (i) monitor a combination of one or more signals indicative of a service brakes holding function, (ii) monitor a combination of one or more signals indicative of a fault condition, and (iii) provide one or more signals to de-energize the normally-energized solenoid to exhaust air pressure in at least some components of the parking brake system and thereby to set park brakes when both signals indicative of a service brakes holding function and signals indicative of a fault condition of the vehicle are detected.