Handling Emergencies

Study questions with answers

8 sample Handling Emergencies questions with the correct answer, a short explanation, and the official handbook reference. Read through them, then take the quiz above.

1. 1. If the low air pressure warning comes on while driving, why is it safer to stop while air still remains in the tanks?

   Correct answer: You can still use the foot brakes for a controlled stop while air lasts

   Controlled braking is only possible while enough air is left in the tanks; if you wait, the spring brakes may come on suddenly, and a heavily loaded vehicle takes a long distance to stop because they do not work on all axles.

   Source: Alabama Commercial Driver License Manual, Section 5 (Air Brakes) - 5.4.7 Low Air Pressure

2. 2. When the low air pressure warning first comes on, what is the safest thing to do?

   Correct answer: Bring the vehicle to a safe stop right away

   You should bring the vehicle to a safe stop right away while you still have enough air to control the brakes, rather than waiting for the spring brakes to apply on their own.

   Source: Alabama Commercial Driver License Manual, Section 5 (Air Brakes) - 5.1.14 Spring Brakes

3. 3. When using the 'controlled braking' method in an emergency, how hard should you press the brakes?

   Correct answer: As hard as you can without locking the wheels

   Controlled braking means applying the brakes as hard as you can without locking the wheels while keeping steering movements small; if the wheels lock or you must steer more, release and then reapply.

   Source: Alabama Commercial Driver License Manual, Section 5 (Air Brakes) - 5.4.3 Emergency Stops

4. 4. A visible low air pressure warning must come on before tank pressure drops below what level?

   Correct answer: Below 55 psi

   Vehicles with air brakes are required to give a warning the driver can see before pressure in the tanks falls under 55 psi.

   Source: Alabama Commercial Driver License Manual, Section 5 (Air Brakes) - 5.1.11 Low Air Pressure Warning

5. 5. What is the main cause of brake fade?

   Correct answer: Excessive heat from overusing the service brakes

   Brake fade comes from excessive heat that builds up when the service brakes are used too much instead of relying on the braking effect of the engine; the heat changes the lining and expands the drums, reducing braking.

   Source: Alabama Commercial Driver License Manual, Section 5 (Air Brakes) - 5.4.5 Brake Fading or Failure

6. 6. While holding a steady speed you notice you must keep increasing the application pressure. What does this most likely mean?

   Correct answer: The brakes are fading and you should slow down and use a lower gear

   Needing more and more application pressure just to hold the same speed is a sign the brakes are fading; the driver should slow down and shift to a lower gear.

   Source: Alabama Commercial Driver License Manual, Section 5 (Air Brakes) - 5.1.10 Application Pressure Gauge

7. 7. Which sequence describes the 'stab braking' method for an emergency stop?

   Correct answer: Apply fully, release when the wheels lock, then reapply once they roll again

   In stab braking you apply the brakes all the way, release them when the wheels lock up, and reapply fully once the wheels begin rolling again, allowing up to a second for them to start rolling.

   Source: Alabama Commercial Driver License Manual, Section 5 (Air Brakes) - 5.4.3 Emergency Stops

8. 8. On a long, steep downgrade, how should the brakes be used?

   Correct answer: As a supplement to engine braking after selecting a low gear

   On a long or steep grade the brakes are only a supplement to the engine's braking effect; once the vehicle is in the proper low gear, brief firm brake applications are used to control speed.

   Source: Alabama Commercial Driver License Manual, Section 5 (Air Brakes) - 5.4.6 Proper Braking Technique