Under which circumstance should caging of the park brake actually be undertaken?
- During every brake application
- During regular maintenance of the brake system
- When the vehicle is parked on a slope
- Only in an emergency ✓
Answer: D. Only in an emergency
Caging the park brake should be done only in an emergency.
Why this is the answer
The handbook’s air brake section treats caging as a way to manually release an applied spring parking brake, and its driving tip says to do it only in an emergency. It also warns that once a spring brake chamber is caged, there is no parking brake force at that wheel. Another passage mentions mechanics using the release for repairs and caging to release brakes for towing when air is lost, but the stated driver rule is emergency use.
Why the other answers are wrong
- A. During every brake application — Caging is a manual release of an applied spring parking brake, not something done during every brake application.
- B. During regular maintenance of the brake system — It is not a routine maintenance step; the handbook limits caging to emergency use, with repair use described for mechanics.
- C. When the vehicle is parked on a slope — Caging removes parking brake force at that wheel, so using it just because the vehicle is parked on a slope would leave that wheel without parking brake force.
Remember it
Emergency only: caging releases the spring, so that wheel loses its parking brake force.