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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. When backing, it is best to:
try to back in the direction of the drift.
back toward the passenger's side when possible.
use only the passenger's side mirror.
use a helper whenever possible.
2. To know how much space you should keep in front of you when driving at speeds below 40 mph, one good rule says you need at least ______ for each ______ of vehicle length.
3 seconds; 50 feet
1 second; 10 feet
2 seconds; 10 feet
1 second; 5 feet
3. You hear a loud "bang" which sounds like a tire blowout. You should:
inspect your tires with your mirrors.
assume you have a tire failure.
check the tires at the next stop.
keep driving as normal.
4. Another name for front-end header boards is:
containerized racks.
head belt.
cargo stopper.
headache racks.
5. Which of the following is most likely to roll over?
The middle trailer of a triple
The front trailer of a double
The rear trailer of a triple
The rear trailer of a double
6. How should you apply the brakes when going down a steep downgrade?
Apply the brakes when you reach the bottom of the downgrade.
You should not brake, and only use engine braking to prevent brake failure.
Apply the brakes as hard as you can without locking the wheels.
Apply the brakes whenever you reach your safe speed, until your speed has been reduced to 5 mph below your safe speed.
7. The application pressure gauge:
protects the tank and the rest of the system from too much pressure.
shows how much air pressure is being applied to the brakes.
stops the compressor from pumping air.
tells you how much pressure is in the air tanks.
8. When driving in extremely hot weather, if the air pressure in the tires is too high, you should:
continue driving.
let air out of the tires to decrease pressure.
call your supervisor.
stop and remain stopped until the tires cool off.
9. You should always try to back toward the driver's side because:
you can watch the rear of your vehicle out the side window.
you can more easily correct any steering errors.
backing toward the left side is more dangerous.
None of the above.
10. For safe handling, the heaviest trailer should be:
the last trailer.
behind the tractor.
the second trailer in a triple.
None of the above.
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NC CDL Doubles Triples Test

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