CDL COMBINATION VEHICLE EXAM, PRACTICE EXAM AND STUDY GUIDE NEWEST 2024 ACTUAL EXAM 300 QUESTIONS AND CORRECT DETAILED ANSWERS WITH (VERIFIED ANSWERS) |ALREADY GRADED A+

When backing under a tractor under a trailer you
should expect:
A. Trailer will be lifted slightly when the tractor backs
under it.
B. End of the kingpin is even with the top of the fifth
wheel. C. Trailer landing gear is fully extended. -
...ANSWER...Trailer will be lifted slightly when the
tractor backs under it.
The driver crosses the air lines when hooking up to an
old trailer. What will happen?
A. If the trailer has no spring brakes, you can drive
away, but you will not have trailer brakes.
B. The brake pedal will work the trailer spring brakes
instead of the air brakes.
C. The hand valve will apply the tractor brakes instead
of the trailer brakes. - ...ANSWER...If the trailer has no
spring brakes, you can drive away, but you will not
have trailer brakes.
You are coupling a tractor to a semi-trailer and have
backed up but are not under it. What should you hook
up before backing under the semi-trailer?
A. The emergency and service air lines.
B. The electrical service cable.
C. Nothing, back up and lock the fifth wheel. -
...ANSWER...The emergency and service air lines.
Air lines on a combination vehicle are often colored to
keep them from getting mixed up. The emergency line
is ____; the service line is ____.
A. Red, blue
B. Blue, red
C. Black, yellow - ...ANSWER...Red, blue
Which of these statements is true?
A. Light vehicles need more braking power to stop
than heavy ones.
B. Always delay braking a heavy vehicle until you have
no other choice.
C. "Bobtail" tractors can take longer to stop than a
combination vehicle loaded to the maximum gross
weight. - ...ANSWER..."Bobtail" tractors can take
longer to stop than a combination vehicle loaded to
the maximum gross weight.
After connecting the air lines, but before backing
under the trailer, you should:
A. Make sure that the trailer brakes are off.
B. Supply air to the trailer system, then pull out the air
supply knob.
C. Walk around the rig to make sure it is clear. -
...ANSWER...Supply air to the trailer system, then pull
out the air supply knob.
The hand valve should be used:
A. To test the trailer brakes.
B. Only when the trailer is fully loaded.
C. Only with the foot brake. - ...ANSWER...To test the
trailer brakes.
The air leakage rate for a combination vehicle (engine
off, brakes off) should be no more than ___ PSI per
minute.
A. 2
B. 3
C. 4 - ...ANSWER...3
The fifth wheel locking lever is not locked after the
jaws close around the kingpin. This means that:
A. You can set the fifth wheel for weight balance.
B. The coupling is not right and should be fixed before
driving the vehicle.
C. The parking lock is off and you may drive away. -
...ANSWER...The coupling is not right and should be
fixed before driving the vehicle.
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:
A. The trailer supply valve to stay open.
B. The tractor to lose all air pressure.
C. The tractor protection valve to close. -
...ANSWER...The tractor protection valve to close.
Semi-trailers made before 1975 that are equipped with
air brakes:
A. Often do not have spring brakes.
B. Usually need to a glad hand converter.C. Are easier
to brake because they are heavier. - ...ANSWER...Often
do not have spring brakes.
Almost half of all truck driver deaths are the result of:
A. Speed.
B. Rollovers.
C. Following too closely. - ...ANSWER...Rollovers.
What statement best explains "crack the whip effect"?
A. When you make a quick lane change or sudden
movement with your steering wheel, the rear trailer
tends to swing out. The force of the rear trailer
becomes amplified, causing it to roll over (rearward
amplification).
B. Your trailer is half full and the cargo is loaded in
the front of the trailer. When you make a sudden
steering wheel movement cargo will tend to forcefully
slide to the back of the trailer, forcing the trailer to
roll over.C. When you make a quick lane change or
sudden movement with your steering wheel, the
tractor tends to rock and sway. The velocity of the
rearmost trailer forces the tractor to roll over before
the trailer. - ...ANSWER...When you make a quick lane
change or sudden movement with your steering
wheel, the rear trailer tends to swing out. The force of
the rear trailer becomes amplified, causing it to roll
over (rearward amplification).