CDL Combination Vehicles Test 4 – Classic Mode

This is CDL Combination Vehicles Test 4 in our original Classic Mode. Simply click in your answer to each CDL practice test question. When you're finished, check your score and results. You can reset the test and retake it as needed.

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1. Why should you lock the tractor glad hands (or dummy couplers) to each other when you are not towing a trailer?

A The connected brake circuit becomes a back up air tank.
B If you did not, you could never build system pressure.
C It will keep dirt and water out of the lines.
D You should never do this.

2. The safety catch for the fifth wheel locking lever must be ____ for a coupling to be complete.

A Under the locking lever
B Over the locking lever
C Through the locking lever
D Inside the locking lever

3. The front trailer supports are up and the trailer is resting on the tractor. Make sure:

A There is enough clearance between the tractor frame and the landing gear.
B There is enough clearance between the tops of the tractor tires and the nose of the trailer.
C Both a and b are correct.
D None of the above.

4. You have a major leak in the service line and you put on the brakes. Service air pressure will escape and cause the:

A Trailer tank pressure to be lost.
B Trailer emergency brakes to come on.
C Tractor spring brakes to lock on.
D None of the above.

5. When backing under a tractor under a trailer you should expect:

A Trailer will be lifted slightly when the tractor backs under it.
B End of the kingpin is even with the top of the fifth wheel.
C Trailer landing gear is fully extended.
D No movement of the trailer if you've done it correctly.

6. You are coupling a tractor to a semi trailer and have backed up but are not under it. What should you hook up before backing under?

A The safety chain.
B The electrical service cable.
C Nothing, back up and lock the fifth wheel.
D The emergency and service air lines.

7. You have coupled with a semi trailer. In what position should you put the front trailer supports before driving away?

A Three turns off the top with the crank handle secured in it?s bracket.
B Fully raised with the crank handle secured in its bracket.
C Raised 1/2 way with the crank handle removed.
D None of the above.

8. Air lines on a combination vehicle are often colored to keep them from getting mixed up. The emergency line is ____; the service line is ____.

A Red, blue
B Blue, red
C Black, yellow
D Depends on the type of trailer

9. Which of these statements is true?

A Light vehicles need more braking power to stop than heavy ones.
B Always delay braking a heavy vehicle until you have no other choice.
C "Bobtail" tractors can take longer to stop than a combination vehicle loaded to the maximum gross weight.
D None of the above.

10. You are coupling a tractor and semi trailer and have connected the air lines. Before backing under the trailer, you should:

A Make sure that the trailer brakes are off.
B Supply air to the trailer system, then pull out the air supply knob to lock the trailer brakes.
C Apply the brakes twice to alert others.
D All of the above.

End of Test #4

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