Handling Emergencies

Study questions with answers

9 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. When the low air warning first comes on while you are driving, what is the safest thing to do?

   Correct answer: Pull over to a safe stop right away, while you still have brake control

   Don't wait for the spring brakes to trip on their own; bring the vehicle to a safe stop while you can still control the brakes.

   Source: Indiana Commercial Driver's License Manual, Section 5 (Air Brakes), 5.1.14 Spring Brakes

2. 2. What is the point of a modulating control valve for the spring brakes?

   Correct answer: To let you bring the spring brakes on gradually if the service brakes quit

   A spring-loaded modulating valve lets you apply the spring brakes gradually so you can still slow down if the service brakes fail.

   Source: Indiana Commercial Driver's License Manual, Section 5 (Air Brakes), 5.1.15 Modulating Control Valves

3. 3. Why is it a mistake to repeatedly pump and release the brake pedal for no reason?

   Correct answer: It can drain air faster than the compressor replaces it, and low pressure means no brakes

   Needless pumping bleeds air out faster than the compressor can rebuild it, and if pressure drops too low the brakes stop working.

   Source: Indiana Commercial Driver's License Manual, Section 5 (Air Brakes), 5.1.7 The Brake Pedal

4. 4. What is the main cause of brake fade on a long downgrade?

   Correct answer: Too much heat from overusing the service brakes instead of leaning on engine braking

   Overusing the service brakes builds excessive heat that changes the linings and expands the drums, which cuts braking force.

   Source: Indiana Commercial Driver's License Manual, Section 5 (Air Brakes), 5.4.5 Brake Fading or Failure

5. 5. What does ABS actually do for you during hard braking?

   Correct answer: It helps you stay in control while braking hard, even if it does not shorten stopping distance

   ABS helps you keep the vehicle under control during hard braking, though it does not necessarily shorten your stopping distance.

   Source: Indiana Commercial Driver's License Manual, Section 5 (Air Brakes), 5.1.16 Antilock Braking Systems (ABS)

6. 6. If one circuit of a dual air brake system loses most of its pressure, what should you expect?

   Correct answer: Either the front or the rear brakes won't work fully, so it takes longer to stop - park safely and get it fixed

   With one circuit low, either the front or the rear brakes won't fully work, so stopping takes longer; bring it to a safe stop and have it repaired.

   Source: Indiana Commercial Driver's License Manual, Section 5 (Air Brakes), 5.2 Dual Air Brake

7. 7. On a tractor or straight truck, the spring brakes come fully on when air pressure drops into which range?

   Correct answer: 20 to 45 psi

   Spring brakes apply fully as pressure falls to roughly 20 to 45 psi, often in the 20 to 30 psi band.

   Source: Indiana Commercial Driver's License Manual, Section 5 (Air Brakes), 5.1.14 Spring Brakes

8. 8. In a hard emergency stop, what does the 'stab braking' method involve?

   Correct answer: Braking all the way, releasing when the wheels lock, then reapplying once they roll again

   Stab braking means applying the brakes fully, releasing them when the wheels lock, and reapplying fully once the wheels start rolling again.

   Source: Indiana Commercial Driver's License Manual, Section 5 (Air Brakes), 5.4.3 Emergency Stops

9. 9. A visible low air pressure warning must switch on before tank pressure falls below what level?

   Correct answer: 55 psi

   The required low-pressure warning has to activate before pressure drops under 55 psi.

   Source: Indiana Commercial Driver's License Manual, Section 5 (Air Brakes), 5.1.11 Low Air Pressure Warning