Emergency Braking and Brake Failure Response
Know what can fail
Brake emergencies usually fall into a few categories: a loss of air pressure, a failed circuit in a dual system, overheated (faded) brakes, or a mechanical failure such as a blown chamber or broken line. Each calls for a different response, so first identify what is happening.
Loss of air pressure
If the low pressure warning sounds and pressure keeps falling, the spring brakes will eventually apply on their own. Do not wait for that to happen in traffic. Downshift, use engine braking, and bring the vehicle to a controlled stop as soon as it is safe. If you still have some braking, use it gently and deliberately.
Faded brakes
If the pedal goes soft and stopping distance grows on a downgrade while the air gauge is steady, the brakes are overheated. Do not pump harder. Shift to a lower gear, use engine braking, and find a place to stop and cool the brakes. Never use a runaway ramp unless it is truly an emergency - but if you have lost control of speed, use it.
Blown tire or mechanical failure
Hold the wheel firmly, avoid hard braking on the affected side, and slow gradually. Signal and move off the road when controlled.
Traps
- Assuming a dual system failure means "no brakes" - you likely still have one circuit.
- Confusing fade with an air leak. Check the gauge: steady air plus weak brakes means fade; falling air means a leak.
- Waiting too long to act. Early, calm action is the correct answer in nearly every scenario question.
Rule of thumb
"Identify, downshift, stop." Figure out which failure you have, use gearing to slow, and get off the road under control.