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

a. red; blue
b. black-yellow
c. blue-red
d. orange-black

16. You are driving a combination vehicle when the trailer breaks away pulling apart both air lines. You would expect the trailer brakes to come on and:

a. the tractor to lose all air pressure.
b. the tractor protection valve to close.
c. the trailer supply valve to stay open.
d. go off about every 2 seconds.

17. How much space should be between the upper and lower fifth wheel after coupling?

a. At least 1/2 inch.
b. About 1/4 inch.
c. Just enough to see light through it.
d. None.

18. After you lock the kingpin into the fifth wheel, you should check the connection by:

a. pulling forward 50 feet turning right and left.
b. backing up with the trailer brakes released.
c. pulling the tractor ahead sharply to release the trailer brakes.
d. pulling the tractor ahead gently with the trailer brakes locked.

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

a. The air circles back getting cleaner each cycle.
b. The brake circuit becomes a backup air tank.
c. It keeps dirt and water out of the lines.
d. All of the above.

20. You are about to back your tractor under a semitrailer. The trailer is at the right height when the:

a. trailer landing gear are fully extended.
b. kingpin is about 1 1/4 inches above the fifth wheel.
c. end of the kingpin is even with the top of the fifth wheel.
d. trailer will be lifted slightly when the tractor backs under it.

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

a. over the locking lever.
b. under the locking lever.
c. straight up.
d. through the locking lever.

Answers: (15)a   (16)b   (17)d   (18)d   (19)c   (20)d   (21)a