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

   Correct answer: The spring brakes do not act on all of the axles

   The spring brakes do not act on all of the axles, so a heavy load has less braking available and needs a long distance to stop.

   Source: Minnesota Commercial Driver's License Manual, Section 5.4.7 - Low Air Pressure

2. 2. If the safety valve lets air escape from the system, what does that tell you?

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

   A safety valve releasing air means something is wrong, and the fault should be corrected by a mechanic.

   Source: Minnesota Commercial Driver's License Manual, Section 5.1.6 - Safety Valve

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

   Correct answer: 20 to 45 psi

   Spring brakes on tractors and straight trucks fully engage once air pressure drops to somewhere in the 20 to 45 psi range.

   Source: Minnesota Commercial Driver's License Manual, Section 5.1.14 - Spring Brakes

4. 4. Which sequence describes stab braking?

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

   Stab braking is applying the brakes fully, releasing when the wheels lock, then reapplying fully once the wheels start rolling again.

   Source: Minnesota Commercial Driver's License Manual, Section 5.4.3 - Emergency Stops

5. 5. Why is repeatedly pressing and releasing the brake pedal for no reason a problem?

   Correct answer: It can release air faster than the compressor can replace it

   Every release lets some air out of the system; fanning the pedal can bleed air off faster than the compressor can replace it, and if pressure gets too low the brakes stop working.

   Source: Minnesota Commercial Driver's License Manual, Section 5.1.7 - The Brake Pedal

6. 6. What is 'controlled braking' during an emergency stop?

   Correct answer: Braking as hard as you can without locking the wheels, using only small steering movements

   Controlled braking means applying the brakes as hard as you can without locking the wheels while keeping steering movements very small.

   Source: Minnesota Commercial Driver's License Manual, Section 5.4.3 - Emergency Stops

7. 7. When the low-air warning first comes on, what is the recommended action?

   Correct answer: Bring the vehicle to a safe stop right away while you can still control the brakes

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

   Source: Minnesota Commercial Driver's License Manual, Section 5.1.14 - Spring Brakes

8. 8. What happens to the spring brakes if a leak lets all the air escape from the system?

   Correct answer: The springs automatically apply the brakes

   When the air that was holding the springs back is gone, the springs automatically apply the brakes.

   Source: Minnesota Commercial Driver's License Manual, Section 5.1.14 - Spring Brakes

9. 9. What is the purpose of a modulating control valve?

   Correct answer: To apply the spring brakes gradually if the service brakes fail

   A modulating valve lets the driver apply the spring brakes gradually, which is useful for keeping control if the service brakes fail.

   Source: Minnesota Commercial Driver's License Manual, Section 5.1.15 - Parking Brake Controls