Handling Emergencies

Study questions with answers

10 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. In a dual air system, what happens if one of the two air systems gets very low on pressure?

   Correct answer: Either the front or rear brakes will not work fully, so it takes longer to stop

   Losing pressure in one system leaves either the front or rear brakes only partly working, which lengthens your stopping distance; guide the truck safely to a halt and have the brakes serviced.

   Source: South Carolina CDL Manual — Section 5.2: Dual Air Brake

2. 2. Why can a heavily loaded vehicle take a long distance to stop once the spring brakes come on?

   Correct answer: Because the spring brakes act on only some of the axles, not all

   Spring brakes don't apply at every axle, so a heavy load can roll a long way before stopping; it is safer to stop while the tanks still have air for the foot brakes.

   Source: South Carolina CDL Manual — Section 5.4.7: Low Air Pressure

3. 3. The low-pressure warning activates while you are underway. What is the correct response?

   Correct answer: Stop and safely park the vehicle as soon as possible

   A low-pressure warning may mean a leak; controlled braking only works while air remains, so stop and park safely as soon as you can, before the spring brakes set at 20 to 45 psi.

   Source: South Carolina CDL Manual — Section 5.4.7: Low Air Pressure

4. 4. The moment the low-pressure warning light and buzzer first activate, what is the safest action to take?

   Correct answer: Stop safely as soon as it activates, while you still control the brakes

   Don't wait for the springs to set on their own; pull over to a safe stop the moment the warning starts, while braking is still under your control.

   Source: South Carolina CDL Manual — Section 5.1.14: Spring Brakes

5. 5. Which of the following describes the 'stab braking' method?

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

   In stab braking you brake all the way, release when the wheels lock, and reapply fully once they start rolling; it can take up to a second for the wheels to roll again after releasing.

   Source: South Carolina CDL Manual — Section 5.4.3: Emergency Stops

6. 6. What causes brake fade?

   Correct answer: Excessive heat from overusing the service brakes

   Overusing the service brakes builds excessive heat that chemically changes the linings and expands the drums, cutting friction so the shoes must travel farther with less force — that is brake fade.

   Source: South Carolina CDL Manual — Section 5.4.5: Brake Fading or Failure

7. 7. In the 'controlled braking' method for an emergency stop, how hard do you apply the brakes?

   Correct answer: Firmly — as much as possible short of locking the wheels

   Controlled braking means applying the brakes as hard as possible short of locking the wheels, keeping steering movements small; if the wheels lock or you must steer more, release and reapply.

   Source: South Carolina CDL Manual — Section 5.4.3: Emergency Stops

8. 8. You notice you must keep applying more pressure on the application gauge just to hold the same speed. What does this most likely mean?

   Correct answer: The brakes are fading

   Needing steadily more application pressure to keep the same speed points to fading brakes; slow down and shift to a lower gear. It can also signal brakes out of adjustment, leaks, or mechanical trouble.

   Source: South Carolina CDL Manual — Section 5.1.10: Application Pressure Gauge

9. 9. On a tractor or straight truck, at about what pressure range will the spring brakes come fully on by themselves?

   Correct answer: 20 to 45 psi

   Spring brakes on tractors and straight trucks come fully on when air pressure falls into the 20 to 45 psi range (often 20 to 30 psi).

   Source: South Carolina CDL Manual — Section 5.1.14: Spring Brakes

10. 10. The safety valve on your air system lets out air. What does this indicate?

    Correct answer: Something is wrong and a mechanic should fix it

    A safety valve releasing air is a sign of a fault in the system, and the problem should be corrected by a mechanic.

    Source: South Carolina CDL Manual — Section 5.1.6: Safety Valve