Braking Technique, Stopping Distance & Downgrades
16 free questions, part of the Air Brakes CDL practice test
Stab braking and controlled braking are the two emergency stopping methods for a vehicle with air brakes. Brake fade happens when heat builds up faster than the brakes can get rid of it, usually from riding the brakes on a long downgrade, and it gets worse the longer you keep your foot on the pedal instead of braking in on/off intervals. ELDT.io's free practice bank has 16 questions on braking technique, stopping distance, and downgrade control.
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Start Class A CDL Theory ($15)Questions about Braking Technique, Stopping Distance & Downgrades
What is stab braking?
Stab braking means applying the brakes hard enough to lock up the wheels, then releasing them completely until they start rolling again, then reapplying. You repeat that until you've stopped. Never reapply the brakes the instant the wheels lock, since it can take a second or more for them to start rolling again.
What is controlled braking?
Controlled braking means applying the brakes as hard as you can without locking the wheels and holding that pressure. If a wheel does lock up, you ease off just enough to get it rolling again, then reapply. It keeps the vehicle more steerable than stab braking throughout the stop.
What causes brake fade?
Brake fade comes from heat. Riding the brakes on a long or steep downgrade builds heat faster than the linings can shed it, and once they get too hot they stop gripping effectively. That's why the correct downgrade technique is to brake hard enough to slow a few mph below your safe speed, then let off completely instead of holding steady pressure.
What does emergency braking mean on a CDL test?
Emergency braking refers to the stab braking and controlled braking methods drivers use to stop a commercial vehicle as fast as possible without losing control. Which one applies to your vehicle depends on how it's set up, but both are built around not letting the wheels stay locked.