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SC CDL Combination Vehicles Practice Questions - South Carolina CDL Combination Vehicles Test Exam
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Question
1
of 25
QUESTION 1 / 25
For the South Carolina Class A CDL combination vehicles test, what is a combination vehicle?
Choose one answer below.
A
A straight truck with cargo loaded in the bed
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B
A truck or tractor pulling one or more trailers
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C
Any commercial vehicle with a GVWR over 10,000 lb
✓
D
A vehicle with both gasoline and diesel engines
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QUESTION 2 / 25
For combination-vehicle safety, which of the following is the most common combination vehicle on U.S. highways?
Choose one answer below.
A
Tractor with a full trailer
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B
Tractor-semi-trailer
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C
Tractor pulling three trailers
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D
Straight truck with a converter dolly
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QUESTION 3 / 25
What does GCWR stand for?
Choose one answer below.
A
Gross Cargo Weight Rating
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B
Gross Combination Weight Rating
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C
General Combined Weight Reference
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D
Government Commercial Weight Regulation
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QUESTION 4 / 25
Under South Carolina and FMCSA CDL class rules, a Class A combination generally has GCWR of at least 26,001 pounds and a towed unit with GVWR over:
Choose one answer below.
A
5,000 lb
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B
8,000 lb
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C
10,000 lb
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D
12,000 lb
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QUESTION 5 / 25
On the South Carolina CDL combination test, what is off-tracking?
Choose one answer below.
A
The trailer drifting sideways on a wet road
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B
The rear wheels of the trailer following a tighter path than the tractor's front wheels in a turn
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C
Loss of tire traction during heavy braking
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D
The vehicle leaving its travel lane on a curve
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QUESTION 6 / 25
On a South Carolina CDL road scenario, you are making a right turn in a tractor-semi-trailer at a city intersection. Because of off-tracking, you should:
Choose one answer below.
A
Turn the wheel as soon as the cab clears the curb
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B
Drive farther into the intersection so the trailer's rear wheels clear the curb
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C
Make the turn as tightly as possible to stay in your lane
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D
Slow down and use the trailer hand valve to stabilize
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QUESTION 7 / 25
For a South Carolina CDL combination vehicle, when making a left turn in a combination vehicle, you should:
Choose one answer below.
A
Make the tightest left turn possible to clear faster
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B
Start in the right-most lane available
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C
Watch for vehicles passing on your left in the lane next to you
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D
Use the trailer hand valve halfway through the turn
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QUESTION 8 / 25
Compared to a straight truck, a combination vehicle's steering response is:
Choose one answer below.
A
Faster and more direct
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B
Delayed and requires smaller, earlier corrections
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C
Identical
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D
Only affected by trailer length, not response time
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QUESTION 9 / 25
On the South Carolina CDL combination test, what is a jackknife?
Choose one answer below.
A
A loose connection between the kingpin and fifth wheel
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B
The tractor and trailer fold against each other at the coupling
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C
A type of converter dolly used with doubles
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D
A skid in which all four trailer tires lose traction simultaneously
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QUESTION 10 / 25
If you start to feel the trailer skidding and swinging out behind you, what is the correct response?
Choose one answer below.
A
Apply the trailer hand valve to slow the trailer
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B
Steer in the same direction as the trailer is swinging
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C
Get off the brakes so the trailer wheels can roll and the trailer can return inline
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D
Use the parking brake to lock the trailer in place
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QUESTION 11 / 25
For combination-vehicle safety, why are empty trailers more prone to brake lock-up than loaded trailers?
Choose one answer below.
A
The brakes are smaller on empty trailers
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B
There is less weight on the tires, so they can lock up more easily
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C
Empty trailers use different brake fluid
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D
Empty trailers run at lower air pressure
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QUESTION 12 / 25
Stopping distance for a combination vehicle is:
Choose one answer below.
A
Shorter than for a straight truck of the same weight
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B
About the same as a passenger car
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C
Significantly longer than for a straight truck
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D
Independent of speed because of trailer brakes
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QUESTION 13 / 25
On a wet, slippery road in a combination vehicle, you should:
Choose one answer below.
A
Reduce speed and increase following distance
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B
Maintain normal speed but use the trailer hand valve
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C
Brake harder than normal to compensate
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D
Drive in the right lane only
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QUESTION 14 / 25
On the South Carolina CDL combination test, what is the kingpin?
Choose one answer below.
A
A locking lever on the fifth wheel
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B
A vertical pin in the trailer apron that locks into the fifth wheel jaws
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C
A bolt that secures the landing gear
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D
The release handle for the trailer brakes
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QUESTION 15 / 25
In South Carolina CDL combination procedures, before backing under a trailer, the locking jaws on the fifth wheel must be:
Choose one answer below.
A
Closed and locked
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B
Open
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C
Removed for inspection
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D
Greased and closed
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QUESTION 16 / 25
Which sequence best matches the South Carolina CDL Manual procedure for coupling a tractor-semitrailer?
Choose one answer below.
A
Connect air lines, then back under, then raise landing gear
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B
Inspect fifth wheel, position tractor, back under, tug test, visual check, connect air and electrical, raise landing gear
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C
Raise landing gear first, then back under, then tug test
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D
Back under, raise landing gear, then connect air lines
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QUESTION 17 / 25
How do you perform the tug test after coupling?
Choose one answer below.
A
Honk the horn and look for vibration
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B
With the trailer brakes set, gently pull the tractor forward in low gear
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C
Drive forward five feet and check the trailer height
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D
Pull the trailer air supply knob and listen for air loss
✓
QUESTION 18 / 25
In South Carolina CDL combination procedures, after the tug test, you should also:
Choose one answer below.
A
Crawl under and visually inspect the locked jaws around the kingpin
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B
Skip the visual check if the tug test passed
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C
Disconnect the air lines to verify the trailer brakes
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D
Apply the parking brake before lowering the landing gear
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QUESTION 19 / 25
There is a visible gap between the trailer apron and the fifth wheel after coupling. What does this likely mean?
Choose one answer below.
A
The coupling is normal
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B
The kingpin may be resting on top of the closed jaws - a dangerous high coupling
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C
The trailer is overloaded
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D
The fifth wheel is properly greased
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QUESTION 20 / 25
What color glad-hand is used for the emergency (supply) line?
Choose one answer below.
A
Blue
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B
Yellow
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C
Red
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D
Green
✓
QUESTION 21 / 25
What color glad-hand is used for the service line?
Choose one answer below.
A
Red
✓
B
Blue
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C
Black
✓
D
Yellow
✓
QUESTION 22 / 25
What happens if the emergency and service glad-hands are cross-connected?
Choose one answer below.
A
The trailer brakes will work normally
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B
The trailer service brakes will not work and the trailer emergency brakes may release without supply
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C
Only the tractor brakes will be affected
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D
The ABS will engage automatically
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QUESTION 23 / 25
The red 8-sided 'Trailer Air Supply' knob on the dash is:
Choose one answer below.
A
Pulled out to supply air to the trailer
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B
Pushed in to supply air to the trailer; pulled out to apply trailer emergency brakes
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C
Always left in the out position when driving
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D
A pressure gauge, not a control
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QUESTION 24 / 25
For a South Carolina CDL combination vehicle, when should you use the trailer hand valve (trolley valve)?
Choose one answer below.
A
As your primary stopping control while driving
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B
Only to test the trailer brakes; not for normal stopping
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C
To park the trailer overnight
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D
On every downhill grade
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QUESTION 25 / 25
The trailer hand valve must NEVER be used:
Choose one answer below.
A
To test the trailer brakes
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B
For parking the trailer or as a parking brake
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C
To slow the trailer for a quick brake check
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D
With the engine running
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