CDL Air Brakes TestUsing Air BrakesMedium
A driver is operating a commercial vehicle with air brakes on a long, steep downgrade. To prevent brake fade and maintain control, what braking technique should be primarily used?
- AConstant, light pressure on the brake pedal.
- BSnub braking: applying brakes firmly until speed is reduced by about 5 mph, then releasing.
- CUsing the parking brake intermittently to slow down.
- DRelying solely on the engine brake for speed control.
Show answer & explanationAnswer & explanation
Correct answer: B. Snub braking: applying brakes firmly until speed is reduced by about 5 mph, then releasing.
Snub braking is the recommended technique for controlling speed on long, steep downgrades. This involves applying the brakes firmly enough to reduce speed by a small amount (e.g., 5 mph) below your 'safe' speed, then releasing them to allow the brakes to cool, and repeating the process as needed. This prevents continuous heat buildup and brake fade.
Why the other options are wrong
- A. Constant, light pressure can lead to continuous heat buildup and brake fade.
- C. The parking brake is for parking, not for slowing a moving vehicle, and can cause loss of control or severe damage.
- D. While engine brakes are helpful, they are often not sufficient alone for steep downgrades and should be used in conjunction with snub braking.
Snub Braking
A technique used on downgrades where brakes are applied firmly for a short period to reduce speed, then released to allow cooling.
- Prevents brake fade by dissipating heat.
- Maintain a safe speed, typically 5 mph below.
- Do not hold brakes down continuously.
Memory trick: Downhill, don't drag; snub it and save your brakes.