CDL Air Brakes TestUsing Air BrakesMedium
A commercial driver is operating a vehicle equipped with air brakes on a gravel road and needs to apply the brakes to slow down. The vehicle does NOT have an Anti-lock Braking System (ABS). Which braking technique is most appropriate to maintain steering control and prevent wheel lock-up?
- APressing the brake pedal firmly until the wheels lock, then immediately releasing and reapplying.
- BApplying full, steady pressure to the brake pedal until the vehicle stops.
- CUsing the parking brake to supplement the service brakes for a quicker stop.
- DApplying the brakes lightly and continuously, allowing the vehicle to gradually slow down.
Show answer & explanationAnswer & explanation
Correct answer: A. Pressing the brake pedal firmly until the wheels lock, then immediately releasing and reapplying.
On slippery surfaces without ABS, stab braking is the recommended technique. This involves applying full brake pressure until the wheels lock, then releasing the brake pedal completely, and reapplying once the wheels begin to roll again. This helps to maintain some steering control while slowing down.
Why the other options are wrong
- B. Applying full, steady pressure will likely cause wheel lock-up and loss of steering control on a gravel road without ABS.
- C. The parking brake should not be used to slow a moving vehicle except in an extreme emergency, as it can cause loss of control.
- D. Light, continuous braking can lead to brake fade or insufficient stopping power in some situations, and may still cause lock-up on very slippery surfaces if not carefully managed.
Stab Braking (Non-ABS)
A braking technique used on slippery surfaces for vehicles without ABS, involving pressing the brake pedal hard until wheels lock, then releasing completely until wheels roll again, and repeating.
- Used on slippery surfaces (e.g., ice, gravel).
- For vehicles NOT equipped with ABS.
- Helps maintain some steering control by preventing prolonged wheel lock-up.
Memory trick: No ABS? On ice, STAB, don't slide, keep control inside!