CDL COMBINATION VEHICLE EXAM, PRACTICE E
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XAM AND STUDY GUIDE NEWEST 2024 ACTUAL EX
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AM 300 QUESTIONS AND CORRECT DETAILED ANS
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WERS WITH (VERIFIED ANSWERS) |ALREADY GRA
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DED A+ n
Why should you lock the tractor glad hands (or dumm
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y couplers) to each other when you are not towing a tr
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ailer?
A. The connected brake circuit becomes a backup air
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tank.
B. If you did not, you could never build system
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pressure.
C. It will keep dirt and water out of the lines. -
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...ANSWER...It will keep dirt and water out of the lines. n n n n n n n n n
For coupling to be completed, the safety catch for the f
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ifth wheel locking lever must be:
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A. Straight up. n
B. Over the locking lever. n n n
C. Through the locking lever. - n n n n
...ANSWER...Over the locking lever.
n n n n
The front trailer supports are up and trailer is resting o
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n the tractor. Make sure:
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A. There is enough clearance between the upper and
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lower fifth wheel. n n
,B. The safety latch is in the unlocked position.
n n n n n n n
C. There is enough clearance between the tractor fra
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me and the landing gear. -
n n n n n
n...ANSWER...There is enough clearance between the t n n n n n n
ractor frame and the landing gear.
n n n n n
You have a major leak in the service line and you put o
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n the brakes. Service air pressure will escape and ca
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use the: n
A. Trailer tank pressure to be lost. n n n n n
B. Trailer emergency brakes to come on. n n n n n
C. Tractor spring brakes to lock on. - n n n n n n
...ANSWER...Trailer emergency brakes to come on. n n n n n
When backing under a tractor under a trailer you shou
n n n n n n n n n
ld expect:
n
A. Trailer will be lifted slightly when the tractor backs
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under it. n
B. End of the kingpin is even with the top of the fifth
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wheel. C. Trailer landing gear is fully extended. -
n n n n n n n n
...ANSWER...Trailer will be lifted slightly when the trac n n n n n n n
tor backs under it.
n n n
The driver crosses the air lines when hooking up to an
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old trailer. What will happen?
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A. If the trailer has no spring brakes, you can drive
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away, but you will not have trailer brakes.
n n n n n n n
,B. The brake pedal will work the trailer spring brakes
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instead of the air brakes. n n n n
C. The hand valve will apply the tractor brakes instead
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of the trailer brakes. - ...ANSWER...If the trailer has no
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spring brakes, you can drive away, but you will not ha
n n n n n n n n n n
ve trailer brakes.
n n
You are coupling a tractor to a semi-
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trailer and have backed up but are not under it. What sh
n n n n n n n n n n n
ould you hook up before backing under the semi-
n n n n n n n n
trailer?
A. The emergency and service air lines.
n n n n n
B. The electrical service cable.
n n n
C. Nothing, back up and lock the fifth wheel. - n n n n n n n n
...ANSWER...The emergency and service air lines. n n n n n
Air lines on a combination vehicle are often colored to k
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eep them from getting mixed up. The emergency line is
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____; the service line is ____.
n n n n n
A. Red, blue n
B. Blue, red n
C. Black, yellow - ...ANSWER...Red, blue n n n n
Which of these statements is true?
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A. Light vehicles need more braking power to stop t
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han heavy ones.
n n
B. Always delay braking a heavy vehicle until you haven n n n n n n n n
no other choice.
n n
, C. "Bobtail" tractors can take longer to stop than a
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combination vehicle loaded to the maximum gross n n n n n n
weight. - n
n...ANSWER..."Bobtail" tractors can take longer to stop n n n n n n
nthan a combination vehicle loaded to the maximum gr
n n n n n n n n
oss weight. n
After connecting the air lines, but before backing unde
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r the trailer, you should:
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A. Make sure that the trailer brakes are off.
n n n n n n n
B. Supply air to the trailer system, then pull out the air
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supply knob. n
C. Walk around the rig to make sure it is clear. -
n n n n n n n n n n
...ANSWER...Supply air to the trailer system, then pull n n n n n n n n
out the air supply knob.
n n n n
The hand valve should be used:
n n n n n
A. To test the trailer brakes.
n n n n
B. Only when the trailer is fully loaded.
n n n n n n n
C. Only with the foot brake. - n n n n n
...ANSWER...To test the trailer brakes.
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The air leakage rate for a combination vehicle (engine o
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ff, brakes off) should be no more than ___ PSI per minut
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e.
A. 2 n
B. 3 n
C. 4 - ...ANSWER...3
n n n
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XAM AND STUDY GUIDE NEWEST 2024 ACTUAL EX
n n n n n n n
AM 300 QUESTIONS AND CORRECT DETAILED ANS
n n n n n n
WERS WITH (VERIFIED ANSWERS) |ALREADY GRA
n n n n n
DED A+ n
Why should you lock the tractor glad hands (or dumm
n n n n n n n n n
y couplers) to each other when you are not towing a tr
n n n n n n n n n n n
ailer?
A. The connected brake circuit becomes a backup air
n n n n n n n n
tank.
B. If you did not, you could never build system
n n n n n n n n n
pressure.
C. It will keep dirt and water out of the lines. -
n n n n n n n n n n
...ANSWER...It will keep dirt and water out of the lines. n n n n n n n n n
For coupling to be completed, the safety catch for the f
n n n n n n n n n n
ifth wheel locking lever must be:
n n n n n
A. Straight up. n
B. Over the locking lever. n n n
C. Through the locking lever. - n n n n
...ANSWER...Over the locking lever.
n n n n
The front trailer supports are up and trailer is resting o
n n n n n n n n n n
n the tractor. Make sure:
n n n n
A. There is enough clearance between the upper and
n n n n n n n n
lower fifth wheel. n n
,B. The safety latch is in the unlocked position.
n n n n n n n
C. There is enough clearance between the tractor fra
n n n n n n n
me and the landing gear. -
n n n n n
n...ANSWER...There is enough clearance between the t n n n n n n
ractor frame and the landing gear.
n n n n n
You have a major leak in the service line and you put o
n n n n n n n n n n n n
n the brakes. Service air pressure will escape and ca
n n n n n n n n n
use the: n
A. Trailer tank pressure to be lost. n n n n n
B. Trailer emergency brakes to come on. n n n n n
C. Tractor spring brakes to lock on. - n n n n n n
...ANSWER...Trailer emergency brakes to come on. n n n n n
When backing under a tractor under a trailer you shou
n n n n n n n n n
ld expect:
n
A. Trailer will be lifted slightly when the tractor backs
n n n n n n n n n
under it. n
B. End of the kingpin is even with the top of the fifth
n n n n n n n n n n n n
wheel. C. Trailer landing gear is fully extended. -
n n n n n n n n
...ANSWER...Trailer will be lifted slightly when the trac n n n n n n n
tor backs under it.
n n n
The driver crosses the air lines when hooking up to an
n n n n n n n n n n n
old trailer. What will happen?
n n n n
A. If the trailer has no spring brakes, you can drive
n n n n n n n n n n
away, but you will not have trailer brakes.
n n n n n n n
,B. The brake pedal will work the trailer spring brakes
n n n n n n n n n
instead of the air brakes. n n n n
C. The hand valve will apply the tractor brakes instead
n n n n n n n n n n
of the trailer brakes. - ...ANSWER...If the trailer has no
n n n n n n n n n
spring brakes, you can drive away, but you will not ha
n n n n n n n n n n
ve trailer brakes.
n n
You are coupling a tractor to a semi-
n n n n n n n
trailer and have backed up but are not under it. What sh
n n n n n n n n n n n
ould you hook up before backing under the semi-
n n n n n n n n
trailer?
A. The emergency and service air lines.
n n n n n
B. The electrical service cable.
n n n
C. Nothing, back up and lock the fifth wheel. - n n n n n n n n
...ANSWER...The emergency and service air lines. n n n n n
Air lines on a combination vehicle are often colored to k
n n n n n n n n n n
eep them from getting mixed up. The emergency line is
n n n n n n n n n n
____; the service line is ____.
n n n n n
A. Red, blue n
B. Blue, red n
C. Black, yellow - ...ANSWER...Red, blue n n n n
Which of these statements is true?
n n n n n
A. Light vehicles need more braking power to stop t
n n n n n n n n
han heavy ones.
n n
B. Always delay braking a heavy vehicle until you haven n n n n n n n n
no other choice.
n n
, C. "Bobtail" tractors can take longer to stop than a
n n n n n n n n n n
combination vehicle loaded to the maximum gross n n n n n n
weight. - n
n...ANSWER..."Bobtail" tractors can take longer to stop n n n n n n
nthan a combination vehicle loaded to the maximum gr
n n n n n n n n
oss weight. n
After connecting the air lines, but before backing unde
n n n n n n n n
r the trailer, you should:
n n n n
A. Make sure that the trailer brakes are off.
n n n n n n n
B. Supply air to the trailer system, then pull out the air
n n n n n n n n n n n
supply knob. n
C. Walk around the rig to make sure it is clear. -
n n n n n n n n n n
...ANSWER...Supply air to the trailer system, then pull n n n n n n n n
out the air supply knob.
n n n n
The hand valve should be used:
n n n n n
A. To test the trailer brakes.
n n n n
B. Only when the trailer is fully loaded.
n n n n n n n
C. Only with the foot brake. - n n n n n
...ANSWER...To test the trailer brakes.
n n n n n
The air leakage rate for a combination vehicle (engine o
n n n n n n n n n
ff, brakes off) should be no more than ___ PSI per minut
n n n n n n n n n n n
e.
A. 2 n
B. 3 n
C. 4 - ...ANSWER...3
n n n
