Sample Commercial Driver License Knowledge Test

(From the 2003 Commercial Driver Handbook)

Directions:  Choose your answer from the three possible answer choices and mark an X in the box across from your choice.  Please do not talk, use any books or notes, or leave the test area with your test before it has been graded; to do so may result in a test failure and your driving privilege may be suspended or revoked.

A list of answers is given at the bottom of this test.

Section 3:  Air Brakes Test

Passing Grade -- 3 errors or less

1. The most important thing to do when a low air pressure warning comes on is:

   1. Upshift and drive to a safe place

   2. Downshift and drive to a safe place

   3. Stop and safely park as soon as possible

    

2. A truck with air brakes going 55 mph would require a stopping distance of::

   1. Less than 100 feet

   2. 100 - 300 feet

   3. More than 300 feet

    

3. Repeatedly pressing and releasing (fanning) the brake pedal may result in:

   1. A loss of brake air pressure

   2. A build up of brake air pressure

   3. No change in brake air pressure

    

4. Your truck has a properly functioning dual air brake system and minimum size air tanks.  The air pressure should build from 85 to 100 psi within:

   1. 30 seconds

   2. 45 seconds

   3. 60 seconds

    

5. The braking power of the spring brakes:

   1. Is not affected by the condition of the service brakes

   2. Depends on the service brakes being in adjustment

   3. Increases when the service brakes are hot

    

6. The application pressure gauge shows how much air pressure you:

   1. Have in teh air tanks

   2. Have in the modulating control valve

   3. Are applying to the brakes

    

7. During normal driving, spring brakes are usually held back by:

   1. Bolts

   2. Spring pressure

   3. Air pressure

    

8. The air brake lag distance at 55 mph on dry pavement adds about _____ feet to your stopping distance.

   1. 12

   2. 52

   3. 32

    

9. What is emergency controlled braking?

   1. You apply the brakes as hard as you can without locking the wheels

   2. You brake as hard as you can, release the brakes when the wheels lock, and reapply the brakes when the wheels start rolling

   3. You apply the hand valve for one second, then push hard on the brake pedal

    

10. If your vehicle has an alcohol evaporator, it is there to:

    1. Rid the wet tank of alcohol that condenses and sits at the bottom

    2. Eliminate the need for daily tank draining

    3. Reduce the risk of ice in air brake valves in cold weather

     

11. How should you check that your service brakes are working properly?

    1. Park on a slight incline, drain off air pressure, set the parking brakes, and check for movement

    2. Park on level ground, chock the wheels, engage the parking brake, and shut the engine off.

    3. Wait for normal air pressure, release the parking brake, move the truck forward slowly, and firmly step on the brake.

     

12. The use of air brakes on downgrqade is only a supplement to the:

    1. Use of the spring brakes

    2. Use of the front brake limiting valve

    3. Braking effect of the engine

     

13. If you must make an emergency stop, brake so you:

    1. Can steer hard while braking hard

    2. Use the hand brake first

    3. Can steer your vehicle in a straight line

     

14. The safety valve is usually set to reduce air pressure at _____ psi.

    1. 50

    2. 100

    3. 150

     

15. The air compressor should stop pumping at about _____ psi.

    1. 100

    2. 125

    3. 150

     

16. What is emergency stab braking?

    1. Press hard on the brake pedal and apply full hand valve until you stop

    2. Use light steady pressure on the brake pedal

    3. Brake hard, release the brakes when the wheels lock, and reapply the brakes when the wheels start rolling

     

17. Your vehicle has a dual air brake system.  If a low air pressure warning comes on for the secondary system, you should:

    1. Stop the vehicle and continue only when the system is fixed

    2. Reduce your speed, and test the remaining system while driving

    3. Reduce your speed, and drive to the nearest garage for repairs

     

18. All air brake equipped vehicles have:

    1. An air supply pressure gauge

    2. An air use gauge

    3. A backup hydraulic system

     

19. When you apply the brakes, the brake shoes/linings are pressed against the:

    1. Brake drum or disc

    2. Slack adjuster

    3. S-Cam

     

20. If your truck's air compressor has its own oil supply, when should you first check the pil level?

    1. Before driving

    2. During your first en route inspection

    3. Immediately after you stop driving