CDL Combination Practice Test
Questions and Answers
After hooking up you should check the fifth wheel connection by - ANSWER-Pulling the
tractor ahead gently with the trailer brakes locked.
After pushing in the trailer supply valve, you should not move the tractor
until air system is? - ANSWER-At normal pressure
Air brake equipped trailers made before 1975 - ANSWER-Usually do not have spring
brakes
Air lines on a combination vehicle are often colored to keep them from getting mixed up.
The emergency line is ____ - ANSWER-Red
How do you supply air to the air tank on the trailer? - ANSWER-By pushing in the trailer
air supply valve.
How far should you crank up the front trailer supports after coupling a semi-trailer? -
ANSWER-Fully raised with the crank handle secured
How much space should be between the upper and lower fifth of the wheel plates? -
ANSWER-None
If the service line disconnects while you're driving, what will happen right away? -
ANSWER-Nothing is likely to happen until you try the brakes.
In normal driving, some drivers use the hand valve before applying the brake pedal to
prevent trailer skids. Which of these statements is true? - ANSWER-It should never be
done.
The fifth wheel locking lever isn't locked after the jaws close around the kingpin. This
means that: - ANSWER-The coupling is not correct and should be corrected before
driving the coupled unit.
The hand valve should be used to park a combination vehicle: - ANSWER-Never
There are two things you can do to prevent a rollover. They are: Keep the cargo as
close to the ground as possible, and: - ANSWER-Reduce speed before entering turns.
When backing under a trailer, you should line up: - ANSWER-Directly in front of the
trailer
Questions and Answers
After hooking up you should check the fifth wheel connection by - ANSWER-Pulling the
tractor ahead gently with the trailer brakes locked.
After pushing in the trailer supply valve, you should not move the tractor
until air system is? - ANSWER-At normal pressure
Air brake equipped trailers made before 1975 - ANSWER-Usually do not have spring
brakes
Air lines on a combination vehicle are often colored to keep them from getting mixed up.
The emergency line is ____ - ANSWER-Red
How do you supply air to the air tank on the trailer? - ANSWER-By pushing in the trailer
air supply valve.
How far should you crank up the front trailer supports after coupling a semi-trailer? -
ANSWER-Fully raised with the crank handle secured
How much space should be between the upper and lower fifth of the wheel plates? -
ANSWER-None
If the service line disconnects while you're driving, what will happen right away? -
ANSWER-Nothing is likely to happen until you try the brakes.
In normal driving, some drivers use the hand valve before applying the brake pedal to
prevent trailer skids. Which of these statements is true? - ANSWER-It should never be
done.
The fifth wheel locking lever isn't locked after the jaws close around the kingpin. This
means that: - ANSWER-The coupling is not correct and should be corrected before
driving the coupled unit.
The hand valve should be used to park a combination vehicle: - ANSWER-Never
There are two things you can do to prevent a rollover. They are: Keep the cargo as
close to the ground as possible, and: - ANSWER-Reduce speed before entering turns.
When backing under a trailer, you should line up: - ANSWER-Directly in front of the
trailer
