CDL Test Combination Test Sample Practice Questions
1. You should not back a tractor under a trailer until the whole air system is:
a. Between 60 and 80 psi
b. At normal pressure
c. Bled down to half the maximum pressure
2. There are two things that a driver can do to prevent a roll over. They are: (1) Keep the cargo as close to the ground as possible; and (2):
a. Make sure that the brakes are properly adjusted.
b. Keep the fifth wheel’s free play as tight as possible.
c. Go slowly around turns.
3. You supply air to the trailer tanks by:
a. Pushing in the trailer air supply valve.
b. Pulling out the trailer air supply valve.
c. Connecting the service line glad hand.
4. If the service air line comes apart while you are driving a combination vehicle but the emergency line stays together, what will happen right away?
a. Nothing is likely to happen until you try to apply the brakes.
b. The trailer’s air tank will exhaust through the open line.
c. The emergency tractor brakes will come on.
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5. 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.
6. 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.
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.
8. The hand valve should be used:
a. To test the trailer brakes.
b. Only when the trailer is fully loaded.
c. Only with the foot brake.
9. Semi trailers made before 1975 that are equipped with air brakes:
a. Often do not have spring brakes.
b. Usually need a glad hand converter.
c. Are easier to brake because they are heavier.
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