CDL - Combination Vehicle Practice Test
questions and answers 2025\2026 A+ Grade
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
questions and answers 2025\2026 A+ Grade
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
