CDL - Combination Vehicle Practice Test
Questions & Correct Answers.
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 - 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 - 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 ...
Page 1 of 9
, 1. cross the air lines,
2. check the air line connections
3. check the electrical cables - 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 - 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 - 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 - 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 - 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?
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Questions & Correct Answers.
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 - 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 - 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 ...
Page 1 of 9
, 1. cross the air lines,
2. check the air line connections
3. check the electrical cables - 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 - 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 - 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 - 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 - 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?
Page 2 of 9
