CDL Combination Practice Test
3 psi - ANS-With the engine off and the brakes released, a combination vehicle air brake system
shouldn't leak more than how many psi in one minute?
At normal pressure - ANS-After pushing in the trailer supply valve, you should not move the
tractor
until air system is?
By pushing in the trailer air supply valve. - ANS-How do you supply air to the air tank on the
trailer?
Directly in front of the trailer - ANS-When backing under a trailer, you should line up:
Fully raised with the crank handle secured - ANS-How far should you crank up the front trailer
supports after coupling a semi-trailer?
Hook up the emergency and service air lines. - ANS-You're hooking up a tractor to a semi-trailer
and have backed up but are not under it. What should you do before backing under the trailer?
If the trailer has no spring brakes, you could drive away, but you wouldn't have trailer brakes. -
ANS-You cross the air lines when hooking up to an old trailer. What will happen?
It keeps dirt and water out of the lines. - ANS-When not pulling a trailer, why is it a good idea to
lock the glad hands together or to a dummy coupler?
It should never be done. - ANS-In normal driving, some drivers use the hand valve before
applying the brake pedal to prevent trailer skids. Which of these statements is true?
Never - ANS-The hand valve should be used to park a combination vehicle:
None - ANS-How much space should be between the upper and lower fifth of the wheel plates?
Nothing is likely to happen until you try the brakes. - ANS-If the service line disconnects while
you're driving, what will happen right away?
Pulling the tractor ahead gently with the trailer brakes locked. - ANS-After hooking up you
should check the fifth wheel connection by
Red - ANS-Air lines on a combination vehicle are often colored to keep them from getting mixed
up. The emergency line is ____
3 psi - ANS-With the engine off and the brakes released, a combination vehicle air brake system
shouldn't leak more than how many psi in one minute?
At normal pressure - ANS-After pushing in the trailer supply valve, you should not move the
tractor
until air system is?
By pushing in the trailer air supply valve. - ANS-How do you supply air to the air tank on the
trailer?
Directly in front of the trailer - ANS-When backing under a trailer, you should line up:
Fully raised with the crank handle secured - ANS-How far should you crank up the front trailer
supports after coupling a semi-trailer?
Hook up the emergency and service air lines. - ANS-You're hooking up a tractor to a semi-trailer
and have backed up but are not under it. What should you do before backing under the trailer?
If the trailer has no spring brakes, you could drive away, but you wouldn't have trailer brakes. -
ANS-You cross the air lines when hooking up to an old trailer. What will happen?
It keeps dirt and water out of the lines. - ANS-When not pulling a trailer, why is it a good idea to
lock the glad hands together or to a dummy coupler?
It should never be done. - ANS-In normal driving, some drivers use the hand valve before
applying the brake pedal to prevent trailer skids. Which of these statements is true?
Never - ANS-The hand valve should be used to park a combination vehicle:
None - ANS-How much space should be between the upper and lower fifth of the wheel plates?
Nothing is likely to happen until you try the brakes. - ANS-If the service line disconnects while
you're driving, what will happen right away?
Pulling the tractor ahead gently with the trailer brakes locked. - ANS-After hooking up you
should check the fifth wheel connection by
Red - ANS-Air lines on a combination vehicle are often colored to keep them from getting mixed
up. The emergency line is ____
