CDL Combination Test questions and answers
2025\2026 A+ Grade
If you cross connect the two air lines the following will result
- correct answer You will not have air going to the trailer brakes
You have coupled with a semi-trailer. In what position should you put the front trailer supports before
driving away?
- correct answer Fully raised with the crank handle secured in its bracket
Th trailer air supply control:
- correct answer Is a red, eight sided knob
A device which connects the service and emergency air lines from the truck to the trailer is called..
- correct answer Glad hands
If one of the glad hands on your blue air line is missing a seal:
- correct answer You might end up with a service line air leak
In order to supply air to the trailer, you must first:
- correct answer Stop engine so you can hear the brakes
The hand valve should be used:
- correct answer To test the trailer brakes
The air leakage rate for a combination vehicle (engine off, brakes on) should not be more than _______
psi per minute
- correct answer 4
When should you use the hand valve to park a combination vehicle?
- correct answer Never
, When you get ready to back under the semi-trailer you should line up
- correct answer Directly in front of the trailer
If the service air line comes apart while you are driving a combination vehicle but the emergency line
stays together, what will happen right away
- correct answer Nothing is likely to happen until you try to apply the brakes
When uncoupling, if you park the trailer at an angle...
- correct answer You could do damage to the landing gear
Which of these statements is true?
- correct answer "Bobtail" tractors can take longer to stop than a combination vehicle loaded to the
maximum gross weight
In normal driving, some drivers use the hand valve before applying the brake pedal to prevent a
jackknife. Which of these statements is true?
- correct answer It should not be done
When you inspect the coupling, check to ensure that:
- correct answer There's a little slack in the air lines
When backing under a tractor under a trailer you should expect:
- correct answer Trailer will be lifted slightly when the tractor back under it
A king pin is:
- correct answer A pin which locks the trailer to the tractor on the fifth wheel
The safety catch for the fifth wheel locking level must be ______ for a coupling to be complete.
- correct answer Over the locking lever
The air leakage rate for a combination vehicle (engine off, brakes off) should be no more than _____ psi
per minute.
- correct answer 3
2025\2026 A+ Grade
If you cross connect the two air lines the following will result
- correct answer You will not have air going to the trailer brakes
You have coupled with a semi-trailer. In what position should you put the front trailer supports before
driving away?
- correct answer Fully raised with the crank handle secured in its bracket
Th trailer air supply control:
- correct answer Is a red, eight sided knob
A device which connects the service and emergency air lines from the truck to the trailer is called..
- correct answer Glad hands
If one of the glad hands on your blue air line is missing a seal:
- correct answer You might end up with a service line air leak
In order to supply air to the trailer, you must first:
- correct answer Stop engine so you can hear the brakes
The hand valve should be used:
- correct answer To test the trailer brakes
The air leakage rate for a combination vehicle (engine off, brakes on) should not be more than _______
psi per minute
- correct answer 4
When should you use the hand valve to park a combination vehicle?
- correct answer Never
, When you get ready to back under the semi-trailer you should line up
- correct answer Directly in front of the trailer
If the service air line comes apart while you are driving a combination vehicle but the emergency line
stays together, what will happen right away
- correct answer Nothing is likely to happen until you try to apply the brakes
When uncoupling, if you park the trailer at an angle...
- correct answer You could do damage to the landing gear
Which of these statements is true?
- correct answer "Bobtail" tractors can take longer to stop than a combination vehicle loaded to the
maximum gross weight
In normal driving, some drivers use the hand valve before applying the brake pedal to prevent a
jackknife. Which of these statements is true?
- correct answer It should not be done
When you inspect the coupling, check to ensure that:
- correct answer There's a little slack in the air lines
When backing under a tractor under a trailer you should expect:
- correct answer Trailer will be lifted slightly when the tractor back under it
A king pin is:
- correct answer A pin which locks the trailer to the tractor on the fifth wheel
The safety catch for the fifth wheel locking level must be ______ for a coupling to be complete.
- correct answer Over the locking lever
The air leakage rate for a combination vehicle (engine off, brakes off) should be no more than _____ psi
per minute.
- correct answer 3
