Quiz: CDL Combination Practice Test Questions!

25 Questions | Total Attempts: 10889

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Quiz: CDL Combination Practice Test Questions!

A combination vehicle is one that connects a tractor to one or more trailers. These types of vehicles are used to transport heavy objects and due to their uniqueness need a different driving license other than the normal commercial one. If you are training to get your CDL the combination test below is for you. Give it a shot and drive safe.


Questions and Answers
  • 1. 
    You are driving a combination vehicle. If the service air line comes apart but the emergency line stays together, what will happen right away?
    • A. 

      The trailer's air tank with exhaust through the open line.

    • B. 

      The emergency trailer brakes will come on.

    • C. 

      Nothing is likely to happen until you try to apply the brakes.

  • 2. 
    If you cannot make a turn without entering another traffic lane, you should:
    • A. 

      Turn wide before you start your turn.

    • B. 

      Turn wide as you complete your turn.

    • C. 

      Not make that turn.

  • 3. 
    When should you use chocks to park a trailer not equipped with spring brakes?
    • A. 

      Never

    • B. 

      Always

    • C. 

      Only when it will be parked on an incline.

  • 4. 
    In general, the higher your truck's "center of gravity", the:
    • A. 

      Easier it is to turn around corners.

    • B. 

      More stable it is when turning.

    • C. 

      Easier it is to turn over.

  • 5. 
    One of the things a driver can do to prevent a rollover is to keep:
    • A. 

      Both hands firmly on the steering wheel.

    • B. 

      The cargo as close to the ground as possible.

    • C. 

      The fifth wheel free play as small as possible.

  • 6. 
    The trailer air supply control (or tractor protection valve control) should automatically close when the air pressure falls between ______ psi.
    • A. 

      20 and 45

    • B. 

      60 and 85

    • C. 

      100 and 125

  • 7. 
    • A. 

      Loaded to full capacity.

    • B. 

      Over loaded.

    • C. 

      Empty.

  • 8. 
    You are driving a combination vehicle. The trailer breaks away and pulls apart both air lines. You would expect the trailer brakes to come on and the:
    • A. 

      Tractor to lose all air pressure.

    • B. 

      Trailer supply valve to stay open.

    • C. 

      Tractor protection valve to close.

  • 9. 
    • A. 

      There is enough clearance between the upper and lower fifth wheel.

    • B. 

      The safety latch is in the unlocked position.

    • C. 

      There is enough clearance between the tractor frame and landing gear.

  • 10. 
    • A. 

      The emergency and service air lines.

    • B. 

      The electrical service cable.

    • C. 

      Nothing. Back up and lock the fifth wheel.

  • 11. 
    Which part of the kingpin should the locking jaws close around?
    • A. 

      The shank.

    • B. 

      The head.

    • C. 

      The base.

  • 12. 
    You should not back a tractor under a trailer until the whole air system is:
    • A. 

      Empty.

    • B. 

      At normal pressure.

    • C. 

      Between 60 and 80 psi.

  • 13. 
    You want to inspect the trailer supports. You should place the tractor transmission in which gear after you have uncoupled the trailer?
    • A. 

      Low reverse.

    • B. 

      Neutral.

    • C. 

      High reverse.

  • 14. 
    What will happen if the air lines are crossed when you hook up to an old trailer with no spring brakes?
    • A. 

      The hand valve applies the tractor brakes instead of the trailer brakes.

    • B. 

      You could drive away with no trailer brakes.

    • C. 

      The brake lights will not come on when you press the brake pedal.

  • 15. 
    After you supply air to the trailer, make sure the air lines are not crossed and the trailer brakes are working. You do this by:
    • A. 

      Turning on the parking brakes from the cab.

    • B. 

      Watching your mirrors to see if the trailer lights come on.

    • C. 

      Applying/releasing the trailer brakes and listening for brake sounds.

  • 16. 
    Which of these statements is true?
    • A. 

      The brake suspension system of combination vehicles work best with a light load.

    • B. 

      Light vehicles need more braking power to stop than heavy ones.

    • C. 

      "Bobtail" tractors can take longer to stop than a combination vehicle.

  • 17. 
    Loss of air pressure in the emergency line causes:
    • A. 

      The relay valves to close.

    • B. 

      An increase in air pressure to the service line.

    • C. 

      The trailer's emergency brakes to come on.

  • 18. 
    Why should you be sure that the fifth wheel plate is greased as required?
    • A. 

      To ensure good electrical connections.

    • B. 

      To prevent steering problems.

    • C. 

      To reduce heat and noise.

  • 19. 
    Glad hands are used to connect the:
    • A. 

      Electric lines from the truck to the trailer.

    • B. 

      Kingpin from the tractor to the locking jaws on the glide side.

    • C. 

      Service and emergency air lines from the truck to the trailer.

  • 20. 
    When should you use the hand valve to park a combination vehicle?
    • A. 

      To park at loading docks.

    • B. 

      To park on a grade.

    • C. 

      Never.

  • 21. 
    A tractor with a(n) ________ trailer requires the shortest stopping distance.
    • A. 

      Empty.

    • B. 

      Lightly loaded.

    • C. 

      Fully loaded.

  • 22. 
    Under good driving conditions, you should leave at least one second of space between your vehicle and the vehicle ahead for every ______ feet of your vehicle's length.
    • A. 

      10

    • B. 

      20

    • C. 

      30

    • D. 

      Option 4

  • 23. 
    When you are uncoupling a loaded trailer, lower the landing gear until it:
    • A. 

      Makes firm contact with the ground.

    • B. 

      Makes contact with the ground and lifts the trailer off of the fifth wheel.

    • C. 

      Just reaches the ground.

  • 24. 
    You have uncoupled a trailer and you want to inspect the landing gear. The tractor should be positioned: 
    • A. 

      With the tractor frame under the trailer.

    • B. 

      Completely clear of the trailer.

    • C. 

      With the fifth wheel directly beneath the kingpin.

  • 25. 
    When checking the trailer's emergency brakes, the tractor protection control valve should be placed in the _____ position.
    • A. 

      Normal

    • B. 

      Neutral

    • C. 

      Emergency