CDL Combination Vehicles Test 4 – Classic Mode

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

Test Score =