Free Combination Vehicles CDL practice questions

Sample questions from this test

1. About how many truck driver deaths in crashes are caused by rollovers?
   1. About one in ten
   2. About one quarter
   3. More than half
   4. Almost none
   Show answer

   More than half

   More than half of truck driver crash deaths result from rollovers.

2. You make a sudden turn while pulling doubles. Which trailer is most likely to tip over?
   1. The first trailer
   2. The rear (last) trailer
   3. Both equally
   4. Neither; only the tractor tips
   Show answer

   The rear (last) trailer

   Because of rearward amplification, the last trailer is the most likely to turn over.

3. Which trailer is most likely to get stuck (hung up) on a raised railroad crossing?
   1. A dry van with normal ground clearance
   2. A lowboy
   3. A flatbed with high clearance
   4. A tank trailer with tandem axles set correctly
   Show answer

   A lowboy

   Low-slung units like lowboys, car carriers, moving vans and possum-belly livestock trailers can hang up.

4. Once the trailer swings out of your lane in a skid:
   1. It is easy to correct with the hand valve
   2. It is very difficult to prevent a jackknife
   3. ABS will always straighten it
   4. You should accelerate hard
   Show answer

   It is very difficult to prevent a jackknife

   Once the trailer leaves your lane, a jackknife is very hard to prevent, so catch it early in the mirrors.

5. While backing, the trailer starts to drift off the proper path. How do you correct it?
   1. Pull the trailer hand valve
   2. Stop and set the parking brake for 1 minute
   3. Turn the top of the wheel away from the drift
   4. Turn the top of the steering wheel toward the drift
   Show answer

   Turn the top of the steering wheel toward the drift

   Fix drift right away: turn the top of the steering wheel toward the side the trailer is drifting to.

6. The tractor protection valve closes automatically when air pressure drops to about:
   1. 60 to 80 psi
   2. 100 to 125 psi
   3. 20 to 45 psi
   4. 5 to 10 psi
   Show answer

   20 to 45 psi

   It closes automatically when pressure is low, in the 20 to 45 psi range.

7. The service line connects to relay valves. What do relay valves do?
   1. Release the spring brakes
   2. Let the trailer brakes apply more quickly
   3. Fill the tractor tanks
   4. Close the tractor protection valve
   Show answer

   Let the trailer brakes apply more quickly

   Relay valves allow the trailer brakes to be applied faster than would otherwise be possible.

8. With an older trailer without spring brakes, crossed air lines and an empty trailer tank, what is the danger?
   1. The trailer will not move at all
   2. You could drive away with no trailer brakes
   3. The tractor brakes will lock
   4. The fifth wheel will unlock
   Show answer

   You could drive away with no trailer brakes

   Without spring brakes and with no tank air, the wheels turn freely, so you could drive off with no trailer brakes.

9. Why should you use wheel chocks when parking a trailer without spring brakes?
   1. Chocks are required only on hills
   2. The air in the trailer tank will eventually leak away and the brakes will release
   3. Chocks keep the ABS working
   4. The fifth wheel may unlock
   Show answer

   The air in the trailer tank will eventually leak away and the brakes will release

   Emergency brakes on these trailers hold only while there is tank air; when it leaks away, there are no brakes.

10. Which statement about ABS is correct?
    1. It increases your normal braking power
    2. It always shortens stopping distance
    3. It helps you keep control during hard braking
    4. It works all the time, even in gentle stops
    Show answer

    It helps you keep control during hard braking

    ABS doesn't necessarily shorten stopping distance, but it helps you keep control in hard braking.

11. What can happen if the fifth wheel plate is not kept greased?
    1. The trailer will be too low
    2. The ABS will fail
    3. Friction can cause steering problems
    4. The air lines will cross
    Show answer

    Friction can cause steering problems

    Without lubrication, friction between tractor and trailer can cause steering problems.

12. How do you check that the trailer is locked onto the tractor (step 11)?
    1. Look at the ABS lamp
    2. Push the trailer air supply knob in
    3. Raise the landing gear slightly and pull forward gently with the trailer brakes locked
    4. Back up hard against the kingpin
    Show answer

    Raise the landing gear slightly and pull forward gently with the trailer brakes locked

    With landing gear slightly off the ground, pull gently forward against the locked trailer brakes.

13. After the landing gear is up and the trailer weight is on the tractor, what clearance must you check?
    1. Between the glad hands and the cab
    2. Between the trailer roof and bridges
    3. Between the rear of the tractor frame and the landing gear
    4. Between the mud flaps and the ground
    Show answer

    Between the rear of the tractor frame and the landing gear

    Check clearance between the tractor frame and landing gear (for sharp turns) and between tractor tires and the trailer nose.

14. When you inspect the coupling from under the trailer, where should the fifth wheel locking lever and safety latch be?
    1. Lever in "open," latch hanging free
    2. Lever in "open," latch removed
    3. Lever halfway, latch beside it
    4. Lever in "lock," safety latch over the lever
    Show answer

    Lever in "lock," safety latch over the lever

    The locking lever must be in the "lock" position with the safety latch in place over it. On some fifth wheels you must set the latch by hand.

15. When uncoupling a gooseneck hitch, after removing the safety pin and clip, what is next?
    1. Lower the trailer jacks onto the truck bed
    2. Disconnect the air lines
    3. Drive forward with the trailer still on the ball
    4. Rotate the handle to release and raise the trailer off the ball
    Show answer

    Rotate the handle to release and raise the trailer off the ball

    Rotate the handle and raise the trailer off the ball; the coupler returns to load position automatically. Then reinstall the pin and clip.