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 is the purpose of the electric heating device found on some automatic air tank drains?

   Correct answer: To keep the automatic drain from freezing in cold weather

   The heaters keep the automatic drain from freezing up in cold weather so it can keep expelling water and oil.

   Source: Minnesota Commercial Driver's License Manual, Section 5.1.4 - Air Tank Drains

2. 2. Why can the brakes still be applied several times even if the compressor quits working?

   Correct answer: The storage tanks hold a reserve of compressed air

   The storage tanks hold a reserve of compressed air, enough to work the brakes a number of times before it runs out.

   Source: Minnesota Commercial Driver's License Manual, Section 5.1.3 - Air Storage Tanks

3. 3. Air brakes on a large commercial vehicle are actually made up of which three separate braking systems?

   Correct answer: The service, parking, and emergency systems

   Air brakes combine a service brake system used for normal driving, a parking brake system, and an emergency brake system that borrows parts of the other two to stop the vehicle if a failure occurs.

   Source: Minnesota Commercial Driver's License Manual, Section 5 - Air Brakes (introduction)

4. 4. What does an antilock braking system (ABS) do?

   Correct answer: It keeps the wheels from locking up during hard braking

   ABS is a computerized system that keeps the wheels from locking up during hard braking so you can keep the vehicle under control.

   Source: Minnesota Commercial Driver's License Manual, Section 5.1.16 - Antilock Braking Systems (ABS)

5. 5. The brake pedal in an air brake vehicle is also known by which other name?

   Correct answer: The foot valve or treadle valve

   The brake pedal is sometimes called the foot valve or the treadle valve.

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

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

   Correct answer: It lowers the chance of ice forming in the valves and other parts

   It adds alcohol to the air system to cut down on the risk of ice forming in the brake valves and other parts during cold weather.

   Source: Minnesota Commercial Driver's License Manual, Section 5.1.5 - Alcohol Evaporator

7. 7. In a dual air system with the engine at operating rpm, pressure should build from 85 to 100 psi within how long?

   Correct answer: 45 seconds

   In a dual air system, pressure should climb from 85 to 100 psi within 45 seconds when the engine is at operating rpm.

   Source: Minnesota Commercial Driver's License Manual, Section 5.3.3 - Check Rate of Air Pressure Buildup

8. 8. Why is it important to completely drain the water that collects in the air tanks?

   Correct answer: In cold weather the water can freeze and cause the brakes to fail

   Compressed air carries water and oil that settle in the tanks; in cold weather the water can freeze and cause the brakes to fail.

   Source: Minnesota Commercial Driver's License Manual, Section 5.1.4 - Air Tank Drains

9. 9. If the air compressor has its own separate oil supply, what should you do before driving?

   Correct answer: Check the compressor's oil level

   A compressor with its own oil supply needs to have its oil level checked before you drive, just like the engine.

   Source: Minnesota Commercial Driver's License Manual, Section 5.1.1 - Air Compressor

10. 10. Before driving a vehicle with a dual air system, you should wait until the compressor builds at least how much pressure in both systems?

    Correct answer: 100 psi

    Allow the compressor to build a minimum of 100 psi in both the primary and secondary systems before you drive.

    Source: Minnesota Commercial Driver's License Manual, Section 5.2 - Dual Air Brake

11. 11. If a vehicle has an alcohol evaporator, do you still need to drain the air tanks daily?

    Correct answer: Yes, daily draining is still needed to remove water and oil

    Yes. The evaporator only fights ice; you still have to drain the tanks daily to get rid of water and oil unless the system has automatic drains.

    Source: Minnesota Commercial Driver's License Manual, Section 5.1.5 - Alcohol Evaporator

12. 12. When checking manual slack adjusters, about how much movement suggests they need adjustment?

    Correct answer: More than about one inch where the push rod attaches

    If a slack adjuster moves more than about one inch where the push rod attaches to it, it probably needs adjustment.

    Source: Minnesota Commercial Driver's License Manual, Section 5.3.2 - Walk-around Inspection