Handling Emergencies

Study questions with answers

11 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 braking system fails, the emergency brake system stops the vehicle by using what?

   Correct answer: Components shared with the service and parking brake systems

   There is no wholly separate emergency system; it borrows parts of the service and parking brakes to bring the vehicle to a stop after a failure.

   Source: Illinois CDL Study Guide — Section 5: Air Brakes (overview)

2. 2. What is a modulating control valve used for?

   Correct answer: Applying the spring brakes gradually if the service brakes fail

   A modulating valve lets you bring the spring brakes on gradually and controllably, which is useful if the service brakes fail.

   Source: Illinois CDL Study Guide — Section 5.1.15: Parking Brake Controls

3. 3. On a tractor or straight truck, spring brakes come fully on in what pressure range, and what should you do beforehand?

   Correct answer: 20 to 45 psi; pull over safely as soon as the low-air warning appears

   Do not wait for the automatic 20-to-45-psi application; stop safely while you still have braking control once the warning first shows.

   Source: Illinois CDL Study Guide — Section 5.1.14: Spring Brakes

4. 4. What does it mean if the safety relief valve starts letting air escape?

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

   The safety valve only vents when pressure is far too high, so any release signals a fault that a mechanic must repair.

   Source: Illinois CDL Study Guide — Section 5.1.6: Safety Valve

5. 5. How is 'controlled braking' performed in an emergency stop?

   Correct answer: Brake as hard as possible without locking the wheels, keeping steering movements small

   Controlled braking means applying the brakes as hard as you can short of lockup, with only small steering inputs; release and reapply if the wheels lock.

   Source: Illinois CDL Study Guide — Section 5.4.3: Emergency Stops

6. 6. On some buses, what does a separate air tank tied to a dual parking control valve allow?

   Correct answer: Briefly releasing the spring brakes so the vehicle can be moved in an emergency

   The separate reservoir can release the spring brakes a few times to reposition the vehicle in an emergency; plan carefully since the air is limited.

   Source: Illinois CDL Study Guide — Section 5.1.15: Parking Brake Controls

7. 7. In freezing weather, what is the specific danger of water left in the air tanks?

   Correct answer: It can freeze and lead to brake failure

   Any water left in the tanks may freeze during cold weather, which can cause the brakes to fail, so daily draining matters.

   Source: Illinois CDL Study Guide — Section 5.1.4: Air Tank Drains

8. 8. Which description matches the 'stab braking' emergency method?

   Correct answer: Brake all the way, release when the wheels lock, then reapply fully once they roll

   In stab braking you apply fully, release when the wheels lock, and reapply when they start rolling again, allowing up to a second for them to roll.

   Source: Illinois CDL Study Guide — Section 5.4.3: Emergency Stops

9. 9. While you are driving normally, what keeps the strong springs of the spring brakes from applying the brakes?

   Correct answer: Air pressure holding the springs back

   Air pressure compresses and holds back the springs while driving; if that air is lost, the springs apply the brakes.

   Source: Illinois CDL Study Guide — Section 5.1.14: Spring Brakes

10. 10. Why is needlessly pumping the brake pedal a bad habit in an air brake vehicle?

    Correct answer: It can bleed air out faster than the compressor rebuilds it, and low pressure disables the brakes

    Every pedal release lets some air escape; pumping needlessly can lower pressure faster than the compressor restores it, and the brakes fail if pressure gets too low.

    Source: Illinois CDL Study Guide — Section 5.1.7: The Brake Pedal

11. 11. If a leak drains all the air from the brake system, what do the spring brakes do?

    Correct answer: Apply the brakes as the springs take over

    Losing all system air lets the springs push the brakes on automatically, which is the emergency and parking function.

    Source: Illinois CDL Study Guide — Section 5.1.14: Spring Brakes