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Safely pulling double and triple trailers requires knowledge and skill. If you want to pull double or triple trailers, you must add the Doubles/Triples (T) endorsement to your Class A CDL. The North Carolina doubles triples test consists of 20 questions. To pass, you must correctly answer at least 16 questions (80%). The NC CDL doubles triples test covers the following sections of the North Carolina CDL Manual: Driving Safely, Air Brakes (if you plan to operate vehicles equipped with air brakes), Combination Vehicles, Doubles and Triples. Take this NC CDL practice test now to prepare for the actual test!
1. The best way to recognize that your trailer has started to skid is:
by feeling the brakes come on.
by recognizing tire failure.
by seeing it in your mirrors.
by opening the window and feeling the front of the mirror.
2. If you are caught in strong winds, you should:
speed up while keeping a strong grip on the steering wheel.
immediately take your foot off the accelerator.
keep a strong grip on the steering wheel and slow down or pull off the roadway.
None of the above.
3. Skids caused by acceleration can usually be stopped by:
speeding up.
applying the brakes firmly.
coming to a complete stop.
taking the foot off the accelerator.
4. Which of the following is a common cause of truck fires?
Under-inflated tires and duals that touch.
loose fuel connections.
Short circuits due to loose connections.
All of the above.
5. To use the controlled braking method in an emergency, you should:
pump the brake pedal 3 times.
apply the brakes when the wheels lock up.
apply your brakes all the way, and release the brakes when the wheels lock up.
apply the brakes as hard as you can without locking the wheels.
6. What can cause poor traction?
Overloading the truck.
Too little weight on the driving axles.
Too much weight on the steering axle.
All of the above.
7. Many large vehicles have convex (curved, "spot, "fisheye") mirrors. Convex mirrors:
are illegal in most states.
misrepresent reality by showing a larger area than flat mirrors.
make things look smaller and farther away than they really are.
None of the above.
8. With the controlled braking method:
you use the parking brake to lock the wheels.
you apply your brakes as hard as possible without locking the wheels.
you lightly tap the brakes.
you apply your brakes all the way and release the brakes when the wheels lock up.
9. An alcohol evaporator:
to hold compressed air.
used to reduce the chance of the front wheels skidding.
is used to reduce the risk of ice in air brake valves and other parts during cold weather.
protects the air brake system from too much pressure.
10. Which of the following is most likely to get stuck on raised railroad crossings?
A low slung unit
A single-axle tractor with no trailer
An empty truck
A single-axle tractor pulling a small trailer
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Doubles Triples NC CDL Test

Number of questions: 20
Correct answers to pass:16
Passing score:80%
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