CDL Combination Vehicles TestDriving Combination Vehicles SafelyEasy
A commercial driver is operating a combination vehicle on a level road. The driver needs to perform an emergency stop due to an unexpected obstacle. Which of the following braking techniques is most effective for a combination vehicle equipped with ABS?
- AApply steady, firm pressure to the brake pedal until the vehicle stops.
- BPump the brakes rapidly to prevent wheel lock-up.
- CRelease the brake pedal if the wheels lock up, then reapply.
- DEngage the parking brake simultaneously with the service brakes.
Show answer & explanationAnswer & explanation
Correct answer: A. Apply steady, firm pressure to the brake pedal until the vehicle stops.
With ABS, the most effective emergency braking technique is to apply steady, firm pressure to the brake pedal. The ABS system will automatically modulate brake pressure to prevent wheel lock-up, allowing the driver to maintain steering control.
Why the other options are wrong
- B. Pumping the brakes is for vehicles without ABS; with ABS, it interferes with the system.
- C. ABS automatically prevents wheel lock-up; releasing the pedal reduces braking effectiveness.
- D. Engaging the parking brake during an emergency stop can cause the drive wheels to lock prematurely, leading to a skid or loss of control, especially with a trailer.
ABS Emergency Braking
For vehicles equipped with Anti-lock Braking Systems (ABS), apply continuous, firm pressure to the brake pedal during an emergency stop.
- ABS automatically prevents wheel lock-up.
- Allows the driver to maintain steering control.
- Pumping the brakes is counterproductive with ABS.
Memory trick: ABS: Stomp and steer, no fear, the system's clear.