Safe Driving Practices

Study questions with answers

12 sample Safe Driving Practices questions with the correct answer, a short explanation, and the official handbook reference. Read through them, then take the quiz above.

1. 1. What does an alcohol evaporator do for an air brake system?

   Correct answer: It reduces the risk of ice forming in the brake valves in cold weather

   It feeds alcohol into the air to lower the chance that ice will form in the valves during cold weather; daily tank draining is still needed.

   Source: Wisconsin Commercial Driver's Manual (BDS356), Section 5.1.5 - Alcohol evaporator

2. 2. The governor stops the compressor from adding air at roughly what pressure?

   Correct answer: About 125 psi, the cut-out level

   That upper limit is the cut-out point, and it sits near 125 psi.

   Source: Wisconsin Commercial Driver's Manual (BDS356), Section 5.1.2 - Air compressor governor

3. 3. On a bus with a separate air tank for releasing the spring brakes, why must you plan your moves carefully?

   Correct answer: There is only enough air to release the spring brakes a few times before it runs out

   That reserve tank holds only enough air to release the spring brakes a few times before it is used up.

   Source: Wisconsin Commercial Driver's Manual (BDS356), Section 5.1.15 - Dual parking control valves

4. 4. What effect does pushing the brake pedal down harder have?

   Correct answer: It applies more air pressure to the brakes

   The pedal is an air valve, so pressing it harder sends more air pressure to the brakes; easing off releases them.

   Source: Wisconsin Commercial Driver's Manual (BDS356), Section 5.1.7 - The brake pedal

5. 5. In a typical S-cam drum brake, how is the vehicle actually slowed?

   Correct answer: The shoes and linings are pressed against the inside of the drum, creating friction

   The turning S-cam spreads the shoes so their linings press on the inside of the drum, and that friction slows the wheel.

   Source: Wisconsin Commercial Driver's Manual (BDS356), Section 5.1.8 - Foundation brakes

6. 6. In a dual air system at operating rpm, pressure should climb from 85 to 100 psi within about how long?

   Correct answer: 45 seconds

   With the engine at operating speed, a dual system should build from 85 to 100 psi in roughly 45 seconds.

   Source: Wisconsin Commercial Driver's Manual (BDS356), Section 5.3.3 - Check rate of air pressure buildup

7. 7. What does the tractor protection valve do if the air supply drops while you are driving?

   Correct answer: It closes on its own

   It closes by itself when the supply falls during driving, protecting the tractor's air.

   Source: Wisconsin Commercial Driver's Manual (BDS356), Section 5.1.15 - Tractor protection valve

8. 8. When you pull hard on an S-cam slack adjuster, about how much movement suggests it needs adjustment?

   Correct answer: More than roughly one inch where the push rod connects

   If the adjuster shifts more than roughly one inch at the point where the push rod attaches, it likely needs adjusting.

   Source: Wisconsin Commercial Driver's Manual (BDS356), Section 5.3.2 - Check slack adjusters on S-cam brakes

9. 9. During a normal stop with a manual transmission, when should you push in the clutch?

   Correct answer: Not until the engine rpm has dropped close to idle

   Hold off on the clutch until the engine rpm has fallen close to idle, then select a starting gear once stopped.

   Source: Wisconsin Commercial Driver's Manual (BDS356), Section 5.4.1 - Normal stops

10. 10. During inspection, a cracked brake drum is considered unsafe when the crack is longer than what?

    Correct answer: More than half of how wide the friction surface is

    A cracked drum counts as a defect once the crack runs more than halfway across how wide the friction surface is.

    Source: Wisconsin Commercial Driver's Manual (BDS356), Section 5.3.2 - Check brake drums (or discs), linings and hoses

11. 11. What does the handbook say about braking with the front wheels?

    Correct answer: Front-wheel braking helps in all conditions and rarely skids, even on ice

    Front-wheel braking helps in every condition, and tests show front skids are unlikely even on ice, so the limiting control should stay in the normal position.

    Source: Wisconsin Commercial Driver's Manual (BDS356), Section 5.1.13 - Front brake limiting valve

12. 12. If your tanks have manually operated drain valves, how often should you drain them?

    Correct answer: At the end of every day you drive

    Manual valves do not empty themselves, so you must open them at the close of each driving day.

    Source: Wisconsin Commercial Driver's Manual (BDS356), Section 5.1.4 - Air tank drains