CDL - Combination Vehicle Practice Test with All Correct
& 100% Verified Answers |Latest Update (Already
Graded A+)
A tractor with a(n) ________ trailer requires the shortest amount of stopping distance .
1. empty
2. fully loaded
3. lightly loaded ✔Correct Answer-fully loaded
The air leakage rate for a combination vehicle ( engine off, brakes on) should not be more than _____
psi per minute .
1. 4
2. 6
3. 2 ✔Correct Answer-4
If you do not do the final air brake check for air leaks and fix them before driving,
1. you could lose your brakes while driving
2. your fuel usage will increase
3. tire pressure will drop ✔Correct Answer-you could lose your brakes while driving
Which part of the kingpin should the locking jaws close around? ✔Correct Answer-The shank
Glad hands are used to connect the ....
1. kingpin from the trailer to the locking jaws of the fifth wheel
2. electrical lines from the tractor to the trailer
3. service and emergency air lines from the truck or tractor to the trailer ✔Correct Answer-service
and emergency air lines from the truck or tractor to the trailer
Trucks roll over more easily when fully loaded and are
1. ten times more likely to roll over in a crash than empty rigs
2. five times more likely to roll over in a crash than empty rigs
3. two times more likely to roll over in a crash than empty rigs ✔Correct Answer-ten times more
likely to roll over in a crash than empty rigs
In general, the higher your trucks center of gravity, the ...
1. easier it is to turn over
2. more stable it is when turning
3. easier it is to turn around corners ✔Correct Answer-easier it is to turn over
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 ...
1. the tractor to lose all air pressure
2. the tractor protection valve to close
3. the trailer supply valve to stay open ✔Correct Answer-the tractor protection valve to close
When you drive a set of doubles, which shut-off valve must be closed in the last trailer?
1. Middle section
2. front section
, 3. back section ✔Correct Answer-back section
The fifth wheel locking lever is not locked after the jaws close around the kingpin. This means that...
1. the parking lock is off and you may drive away
2. the trailer will not swivel on the fifth wheel
3. the coupling is not right and should be fixed before you drive the coupled unit ✔Correct Answer-
the coupling is not right and should be fixed before you drive the coupled unit
What gear should the tractor engine be in after you uncouple the trailer and are inspecting the
trailer?
1. neutral
2. low reverse
3. high reverse ✔Correct Answer-neutral
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 ..
1. lifting the brake pedal
2. applying and releasing the trailer brakes and listening for brake sounds
3. turning on the parking brake from the cab ✔Correct Answer-applying and releasing the trailer
brakes and listening for brake sounds
If the brakes did not release when you pushed the trailer air supply valve, you should ...
1. cross the air lines,
2. check the air line connections
3. check the electrical cables ✔Correct Answer-check the air line connections
You have a major leak in the service line, and you apply the brakes. Service air pressure will escape
and cause the
1. trailer tank pressure to be lost
2. trailer emergency brakes to come on
3. tractor spring brakes to lock on ✔Correct Answer-trailer emergency brakes to come on
You are uncoupling a trailer. After you shut off the trailer air supply and lock the trailer brakes, you
should
1. immediately apply your tractor parking brakes
2. begin to lower the trailer landing gear
3. back up gently and ease pressure on the fifth wheel locking jaws ✔Correct Answer-back up
gently to ease pressure on the fifth wheel locking jaws
When should you use the hand valve to park a combination vehicle?
1. To park at loading docks
2. To park on a grade
3. never ✔Correct Answer-Never
The front trailer supports are up, and the trailer is resting on the tractor. Make sure that
1. there is enough clearance between the upper and lower fifth wheel
2. there is enough clearance between the tractor frame and the landing gear
3. the safety latch is in the unlocked position ✔Correct Answer-there is enough clearance between
the tractor frame and the landing gear
The trailer hand valve works the trailer brakes. Which of these statements is true?
& 100% Verified Answers |Latest Update (Already
Graded A+)
A tractor with a(n) ________ trailer requires the shortest amount of stopping distance .
1. empty
2. fully loaded
3. lightly loaded ✔Correct Answer-fully loaded
The air leakage rate for a combination vehicle ( engine off, brakes on) should not be more than _____
psi per minute .
1. 4
2. 6
3. 2 ✔Correct Answer-4
If you do not do the final air brake check for air leaks and fix them before driving,
1. you could lose your brakes while driving
2. your fuel usage will increase
3. tire pressure will drop ✔Correct Answer-you could lose your brakes while driving
Which part of the kingpin should the locking jaws close around? ✔Correct Answer-The shank
Glad hands are used to connect the ....
1. kingpin from the trailer to the locking jaws of the fifth wheel
2. electrical lines from the tractor to the trailer
3. service and emergency air lines from the truck or tractor to the trailer ✔Correct Answer-service
and emergency air lines from the truck or tractor to the trailer
Trucks roll over more easily when fully loaded and are
1. ten times more likely to roll over in a crash than empty rigs
2. five times more likely to roll over in a crash than empty rigs
3. two times more likely to roll over in a crash than empty rigs ✔Correct Answer-ten times more
likely to roll over in a crash than empty rigs
In general, the higher your trucks center of gravity, the ...
1. easier it is to turn over
2. more stable it is when turning
3. easier it is to turn around corners ✔Correct Answer-easier it is to turn over
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 ...
1. the tractor to lose all air pressure
2. the tractor protection valve to close
3. the trailer supply valve to stay open ✔Correct Answer-the tractor protection valve to close
When you drive a set of doubles, which shut-off valve must be closed in the last trailer?
1. Middle section
2. front section
, 3. back section ✔Correct Answer-back section
The fifth wheel locking lever is not locked after the jaws close around the kingpin. This means that...
1. the parking lock is off and you may drive away
2. the trailer will not swivel on the fifth wheel
3. the coupling is not right and should be fixed before you drive the coupled unit ✔Correct Answer-
the coupling is not right and should be fixed before you drive the coupled unit
What gear should the tractor engine be in after you uncouple the trailer and are inspecting the
trailer?
1. neutral
2. low reverse
3. high reverse ✔Correct Answer-neutral
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 ..
1. lifting the brake pedal
2. applying and releasing the trailer brakes and listening for brake sounds
3. turning on the parking brake from the cab ✔Correct Answer-applying and releasing the trailer
brakes and listening for brake sounds
If the brakes did not release when you pushed the trailer air supply valve, you should ...
1. cross the air lines,
2. check the air line connections
3. check the electrical cables ✔Correct Answer-check the air line connections
You have a major leak in the service line, and you apply the brakes. Service air pressure will escape
and cause the
1. trailer tank pressure to be lost
2. trailer emergency brakes to come on
3. tractor spring brakes to lock on ✔Correct Answer-trailer emergency brakes to come on
You are uncoupling a trailer. After you shut off the trailer air supply and lock the trailer brakes, you
should
1. immediately apply your tractor parking brakes
2. begin to lower the trailer landing gear
3. back up gently and ease pressure on the fifth wheel locking jaws ✔Correct Answer-back up
gently to ease pressure on the fifth wheel locking jaws
When should you use the hand valve to park a combination vehicle?
1. To park at loading docks
2. To park on a grade
3. never ✔Correct Answer-Never
The front trailer supports are up, and the trailer is resting on the tractor. Make sure that
1. there is enough clearance between the upper and lower fifth wheel
2. there is enough clearance between the tractor frame and the landing gear
3. the safety latch is in the unlocked position ✔Correct Answer-there is enough clearance between
the tractor frame and the landing gear
The trailer hand valve works the trailer brakes. Which of these statements is true?
