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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 Iowa doubles triples test consists of 20 questions. To pass, you must correctly answer at least 16 questions (80%). The IA CDL doubles triples test covers the following sections of the Iowa CDL Manual: Driving Safely, Air Brakes (if you plan to operate vehicles equipped with air brakes), Combination Vehicles, Doubles and Triples. Take this IA CDL practice test now to prepare for the actual test!
1. You should be especially alert for drunk drivers:
late at night.
in the morning.
around shopping areas.
2. When you push in the red trailer air supply knob, this will:
open the emergency line shut-off valve at the rear of the last trailer.
supply air to the emergency supply lines.
disconnect the air lines from the trailer.
3. In your mirror, you see a car approaching from the rear. The next time you check your mirror, you don't see the car. If you wish to change lanes, you should:
wait until you are sure the car isn't in your blind spot.
assume the car left the roadway and change lanes as normal.
ease into the other lane slowly so the other car can get out of the way.
4. If you're feeling tired while driving you should:
eat something.
drink coffee.
stop driving and get some rest.
5. While crossing railroad tracks, you should:
shift up.
not shift gears.
shift down.
6. The parking brake:
should be used when driving in bad weather.
should be used when you need to apply the brakes firmly.
should be used whenever you park.
7. How can you tell if a converter dollie has ABS?
There is an ABS plaque on the right side of the dolly.
There is a red lamp on the left side of the dolly.
There is a yellow lamp on the left side of the dolly.
8. Radial and bias-ply tires:
should be used together.
should be used together only when driving in packed snow.
should not be used together.
9. Air brakes use ________ to make the brakes work.
compressed gas cylinders
compressed gases
compressed air
10. Hanging meat in a refrigerated truck:
can be a very unstable load.
should never be transported.
will not affect safe driving ability.
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IA CDL Doubles Triples Test

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