CDL COMBINATION PRACTICE TEST
QUESTIONS AND ANSWERS
mYou'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? - Hook up the emergency and service air lines.
After pushing in the trailer supply valve, you should not move the tractor
until air system is? - At normal pressure
There are two things you can do to prevent a rollover. They are: Keep the cargo as close to the ground as
possible, and: - Reduce speed before entering turns.
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? - 3 psi
The fifth wheel locking lever isn't locked after the jaws close around the kingpin. This means that: - The
coupling is not correct and should be corrected before driving the coupled unit.
You cross the air lines when hooking up to an old trailer. What will happen? - If the trailer has no spring
brakes, you could drive away, but you wouldn't have trailer brakes.
How far should you crank up the front trailer supports after coupling a semi-trailer? - Fully raised with
the crank handle secured
Air brake equipped trailers made before 1975 - Usually do not have spring brakes
The hand valve should be used to park a combination vehicle: - Never
Air lines on a combination vehicle are often colored to keep them from getting mixed up. The emergency
line is ____ - Red
How do you supply air to the air tank on the trailer? - By pushing in the trailer air supply valve.
In normal driving, some drivers use the hand valve before applying the brake pedal to prevent trailer
skids. Which of these statements is true? - It should never be done.
You're hooking up a tractor and semi-trailer, and you've connected both air lines. Before backing under
the trailer, you should: - Supply air to the trailer system, then pull out the air supply knob to lock the
trailer brakes
When backing under a trailer, you should line up: - Directly in front of the trailer
If the service line disconnects while you're driving, what will happen right away? - Nothing is likely to
happen until you try the brakes.
QUESTIONS AND ANSWERS
mYou'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? - Hook up the emergency and service air lines.
After pushing in the trailer supply valve, you should not move the tractor
until air system is? - At normal pressure
There are two things you can do to prevent a rollover. They are: Keep the cargo as close to the ground as
possible, and: - Reduce speed before entering turns.
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? - 3 psi
The fifth wheel locking lever isn't locked after the jaws close around the kingpin. This means that: - The
coupling is not correct and should be corrected before driving the coupled unit.
You cross the air lines when hooking up to an old trailer. What will happen? - If the trailer has no spring
brakes, you could drive away, but you wouldn't have trailer brakes.
How far should you crank up the front trailer supports after coupling a semi-trailer? - Fully raised with
the crank handle secured
Air brake equipped trailers made before 1975 - Usually do not have spring brakes
The hand valve should be used to park a combination vehicle: - Never
Air lines on a combination vehicle are often colored to keep them from getting mixed up. The emergency
line is ____ - Red
How do you supply air to the air tank on the trailer? - By pushing in the trailer air supply valve.
In normal driving, some drivers use the hand valve before applying the brake pedal to prevent trailer
skids. Which of these statements is true? - It should never be done.
You're hooking up a tractor and semi-trailer, and you've connected both air lines. Before backing under
the trailer, you should: - Supply air to the trailer system, then pull out the air supply knob to lock the
trailer brakes
When backing under a trailer, you should line up: - Directly in front of the trailer
If the service line disconnects while you're driving, what will happen right away? - Nothing is likely to
happen until you try the brakes.
