CDL Combination Vehicles TestCombination Vehicle Air BrakesMedium
During an emergency stop in a combination vehicle equipped with ABS, the driver should:
- ARelease the brake pedal if the wheels begin to lock up.
- BApply firm, steady pressure to the brake pedal.
- CUse the trailer hand valve to control trailer braking independently.
- DPump the brakes rapidly to prevent wheel lock-up.
Show answer & explanationAnswer & explanation
Correct answer: B. Apply firm, steady pressure to the brake pedal.
With ABS, the system automatically modulates brake pressure to prevent wheel lock-up. The driver's role is to apply firm, steady pressure to the brake pedal and steer to safety, allowing ABS to do its job.
Why the other options are wrong
- A. Releasing the brake pedal negates the ABS function and reduces braking power during an emergency.
- C. The trailer hand valve is for testing or preventing trailer skids, not for emergency stops with ABS.
- D. Pumping the brakes is for vehicles without ABS; it interferes with ABS function.
ABS Emergency Braking Technique
In a combination vehicle with ABS, the correct technique for an emergency stop is to apply firm, steady pressure to the brake pedal and steer to maintain control, allowing the ABS to prevent wheel lock-up.
- ABS handles wheel lock-up automatically.
- Pumping brakes interferes with ABS.
- Focus on steering to safety.
Memory trick: ABS means 'Always Brake Steady', then Steer clear.