Air Brake Test Air Brake Driving Techniques & Vehicle Control 1 — Questions and Answers
Question 1: When driving downhill with air brakes, what is the recommended braking technique to prevent brake fade?
- Continuous light brake pressure throughout the descent
- Snub braking — apply firm pressure, release, then repeat (Correct answer)
- Full brake application until the vehicle slows to the desired speed
- Engine braking only without touching the service brakes
Correct answer: Snub braking — apply firm pressure, release, then repeat
Snub braking allows brakes to cool between applications, preventing the overheating that causes brake fade.
Question 2: What is 'brake fade' and when does it most commonly occur?
- Loss of air pressure due to a system leak
- Reduced braking effectiveness caused by overheated friction materials (Correct answer)
- Automatic reduction of brake force by the ABS system
- Gradual wear of brake linings over tens of thousands of miles
Correct answer: Reduced braking effectiveness caused by overheated friction materials
Brake fade occurs when friction materials overheat, reducing their ability to create the friction needed to slow the vehicle.
Question 3: What should you do BEFORE starting down a long, steep downhill grade?
- Shift to a higher gear to maintain momentum
- Test brakes and select an appropriate low gear before the descent begins (Correct answer)
- Release air pressure to reduce unnecessary brake wear
- Increase following distance only and descend in a high gear
Correct answer: Test brakes and select an appropriate low gear before the descent begins
Selecting the correct low gear before the descent uses engine braking to help control speed, reducing reliance on service brakes.
Question 4: What is 'stab braking' and when is it used?
- Lightly tapping the brake pedal multiple times to slow gradually
- Applying full brake pressure until wheels lock, then fully releasing to restore steering, repeating as needed (Correct answer)
- Using the parking brake in combination with service brakes for emergency stops
- Applying brakes only to the rear axle to keep the front wheels free for steering
Correct answer: Applying full brake pressure until wheels lock, then fully releasing to restore steering, repeating as needed
Stab braking is a technique for vehicles without ABS that applies full pressure until lockup, then releases to restore steering control.
Question 5: What should you do if your brakes become dangerously hot after a long downhill grade?
- Apply the parking brake briefly to help them cool faster
- Pull over and allow brakes to cool naturally through rest before continuing (Correct answer)
- Drive faster to create more airflow over the brake drums
- Pour water on the drums immediately to speed up cooling
Correct answer: Pull over and allow brakes to cool naturally through rest before continuing
Hot brakes must cool naturally through rest; continuing to drive with overheated brakes risks complete brake failure.
Question 6: On a vehicle without ABS, how should you apply air brakes to avoid wheel lockup during a hard stop?
- Apply maximum brake pressure immediately for the shortest stopping distance
- Pump the brakes rapidly the same way as hydraulic brakes
- Apply firm, steady pressure and ease off slightly if wheels begin to lock (Correct answer)
- Use only the engine brake and avoid the service brakes when stopping quickly
Correct answer: Apply firm, steady pressure and ease off slightly if wheels begin to lock
Steady controlled pressure that avoids locking the wheels is the correct technique, allowing the driver to steer while stopping.
Air Brake Test Air Brake Driving Techniques & Vehicle Control 1
When driving downhill with air brakes, what is the recommended braking technique to prevent brake fade?