Combination Vehicles Practice Test Directions

Combination Vehicles Practice Test Directions
Combination Vehicles Practice Test
Directions: Read each question carefully and select the answer that best answers
the question.
NOTE: This test must be taken by all applicants for a “Class A” CDL.
1. Air lines on a combination vehicle are often colored to keep from getting
them mixed up. The emergency line is:
A.
B.
C.
D.
Red
Black
Blue
Orange
2. There are two things that a driver can do to prevent a rollover. They are:
Keep the cargo as close to the ground as possible, and:
A.
B.
C.
D.
Make sure that the brakes are adjusted properly
Keep both hands firmly on the steering wheel
Reduce speed before entering turns
Keep the fifth wheel free-play loose
3. If the service line disconnects while you’re driving, what will happen right
away?
A.
B.
C.
D.
The emergency tractor brakes will come on
The trailer’s air tank will exhaust through the open line
The emergency trailer brakes will come on
Nothing is likely to happen until you try the brakes
4. How do you supply air to the air tank on the trailer?
A.
B.
C.
D.
By pushing in the trailer air supply valve
By pulling out the trailer air supply valve
By connecting the emergency line glad hand
By applying the trolley valve
5. 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?
A.
B.
C.
D.
1 psi
2 psi
3 psi
4 psi
6. You’re hooking a tractor to a semi-trailer and have backed up but are not
under it. What should you do before backing under the trailer?
A.
B.
C.
D.
Hook up the electrical service cable
Hook up the emergency and service air lines
Connect the ground cable
Nothing, back up and secure the fifth wheel to the trailer
7. The fifth wheel locking lever is not locked after the jaws close around the
kingpin. This means that:
A.
B.
C.
D.
The trailer will not swing on the fifth wheel
You cannot set the fifth wheel for proper weight distribution
The hand valve is released and you may drive away
The coupling is not correct and should be corrected before driving the
coupled unit
8. After pushing in the trailer supply valve, you should not move the tractor
until the whole air system is:
A.
B.
C.
D.
Charging
At normal pressure
Bled down to half the maximum pressure
Between 50 and 60 psi
9. You cross the air lines when hooking up to an old trailer. What will happen?
A. The hand valve will apply the tractor brakes instead of the trailer brakes
B. The brake pedal will work the trailer spring brakes instead of the trailer
brakes
C. If the trailer has no spring brakes, you could drive away but you wouldn’t
have trailer brakes
D. The brake lights will not come on when the brake pedal is pressed
10. How far should you crank up the front trailer supports (dollies) after
coupling a semi-trailer?
A.
B.
C.
D.
Raised ½ way with the crank handle secured
Raised ¾ way with the crank handle removed
Fully raised with the crank handle secured
Three turns off the top with the crank handle secured in its bracket
11. You’re driving a combination vehicle when the trailer breaks away and pulls
apart the air lines. You should expect the trailer brakes to apply and:
A.
B.
C.
D.
The tractor to lose all air pressure
The tractor brakes to keep working properly
The trailer supply valve to stay open
The tractor brakes to lock up
12. The hand valve should be used to park a combination vehicle:
A.
B.
C.
D.
When you park at loading docks
When you are parking for less than one hour
When parking on a steep grade
Never
13. Air brake equipped trailers made before 1975:
A.
B.
C.
D.
Usually do not have spring brakes
Are easier to stop than newer trailers because they are heavier
Usually need a glad hand converter
Cannot be operated on interstate highways
14. In normal driving, some drivers use the trolley (hand) valve before the brake
pedal in order to prevent trailer skids. Which of these statements is true?
A.
B.
C.
D.
It should never be done
It results in less skidding than using the brake pedal alone
It lets the driver steer with both hands
It is the best way to brake in a straight line
15. When backing up under a trailer, you should line up:
A.
B.
C.
D.
About 15 degrees off the line of the trailer
The right mirror along the right edge of the trailer
Directly in front of the trailer
The edge of the tractor tires with the yellow line on the pavement
16. You’re hooking up a tractor and semi-trailer, and you’ve connected both air
lines. Before backing under the trailer, you should:
A. Pull forward to test glad hand connections
B. Supply air to the trailer system, then pull out the air supply knob to lock
the trailer brakes
C. Make sure that the trailer brakes are off
D. Blow the horn twice to alert others
17. When hooking up a tractor to a trailer, you’ll know the trailer is at the right
height when the:
A.
B.
C.
D.
Trailer dolly wheels are fully extended
Kingpin is about 2-¼ inches above the fifth wheel
Beginning of the kingpin is even with the top of the lower fifth wheel
Coupling surface of the trailer is just below the middle of the tractor fifth
wheel
18. When not pulling a trailer, why is it a good idea to lock the glad hands
together or to a dummy coupler?
A.
B.
C.
D.
It keeps air from escaping
The brake circuit becomes a secondary air tank
It keeps dirt and water out of the lines
All of the above
19. How much space should be between the upper and the lower fifth wheel
plates?
A.
B.
C.
D.
About 1 inch
About ½ inch
About ¼ inch
None
20. After hooking up, you should check the fifth wheel connection by:
A.
B.
C.
D.
Driving away at 20 mph and pulling down the trailer hand valve
Backing up with the trailer brakes released
Pulling the tractor ahead sharply to release the trailer brakes
Pulling the tractor ahead gently with the trailer brakes locked
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