CDL Combination Vehicles TestDriving Combination Vehicles SafelyHard
You are driving a combination vehicle on a downhill grade and notice your service brakes are becoming less effective (brake fade). What is the appropriate immediate action?
- ADownshift to a lower gear to increase engine braking and apply stab braking.
- BApply the parking brake firmly to bring the vehicle to a stop.
- CIncrease speed to reduce the load on the brakes.
- DShift to a higher gear to reduce engine RPMs.
Show answer & explanationAnswer & explanation
Correct answer: A. Downshift to a lower gear to increase engine braking and apply stab braking.
Brake fade indicates overheating. Downshifting to a lower gear maximizes engine braking, taking strain off the service brakes. Stab braking (firm, short applications) helps dissipate heat while still providing stopping power without continuous friction.
Why the other options are wrong
- B. Applying the parking brake while moving, especially on a downgrade, can lock the drive wheels, causing a violent jackknife or loss of control, and it's not designed for emergency stopping at speed.
- C. Increasing speed will only exacerbate the problem, making the brakes work harder and increasing the risk of complete failure.
- D. Shifting to a higher gear reduces engine braking, placing more reliance on the already failing service brakes.
Brake Fade Recovery
Actions to take when service brakes become less effective due to overheating, to regain stopping power and control.
- Recognize signs of brake fade (less stopping power, burning smell).
- Downshift immediately to a lower gear.
- Use stab braking (firm, short applications) if service brakes still respond.
- Look for an escape ramp or safe runaway lane if available.
- Stop and allow brakes to cool completely.
Memory trick: Fade means downshift, stab, and pray for an escape ramp.