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CDL - Combination Vehicle Practice Test Questions And Answers
Question 1: A tractor with a(n) ________ trailer requires the
shortest amount of stopping distance.
CORRECT ANSWER : fully loaded
Question 2: The air leakage rate for a combination vehicle (
engine off, brakes on) should not be more than _____ psi per minute.
CORRECT ANSWER : 4
Question 3: If you do not do the final air brake check for air
leaks and fix them before driving,
CORRECT ANSWER : you could lose your brakes while
driving
Question 4: Which part of the kingpin should the locking jaws
close around?
CORRECT ANSWER : The shank
Question 5: Glad hands are used to connect the ....
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CORRECT ANSWER : service and emergency air lines from the
truck or tractor to the trailer
Question 6: Trucks roll over more easily when fully loaded and
are
CORRECT ANSWER : ten times more likely to roll over in a
crash than empty rigs
Question 7: In general, the higher your trucks center of gravity,
the ...
CORRECT ANSWER : easier it is to turn over
Question 8: 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 ...
CORRECT ANSWER : the tractor protection valve to close
Question 9: When you drive a set of doubles, which shut-off
valve must be closed in the last trailer?
CORRECT ANSWER : back section
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Question 10: The fifth wheel locking lever is not locked after the
jaws close around the kingpin. This means that...
CORRECT ANSWER : the coupling is not right and should be
fixed before you drive the coupled unit
Question 11: What gear should the tractor engine be in after you
uncouple the trailer and are inspecting the trailer?
CORRECT ANSWER : neutral
Question 12: After you supply air to the trailer, make sure the air
lines are not crossed and the trailer brakes are working. This is done by ..
CORRECT ANSWER: applying and releasing the trailer brakes
and listening for brake sounds
Question 13: If the brakes did not release when you pushed the
trailer air supply valve, you should ...
CORRECT ANSWER : check the air line connections
Question 14: You have a major leak in the service line, and you
apply the brakes. Service air pressure will escape and cause the
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CORRECT ANSWER : trailer emergency brakes to come on
Question 15: You are uncoupling a trailer. After you shut off the
trailer air supply and lock the trailer brakes, you should
CORRECT ANSWER : back up gently to ease pressure on the
fifth wheel locking jaws
Question 16: When should you use the hand valve to park a
combination vehicle?
CORRECT ANSWER : Never
Question 17: The front trailer supports are up, and the trailer is
resting on the tractor. Make sure that
CORRECT ANSWER : there is enough clearance between the
tractor frame and the landing gear
Question 18: The trailer hand valve works the trailer brakes.
Which of these statements is true?