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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. Which of the following is NOT correct? Anti-lock brakes:
give drivers more control over the vehicle during braking.
help drivers avoid skids caused by over braking.
require drivers to apply the brakes as hard as they can without locking the wheels.
2. 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.
tells you how much pressure is in the air tanks.
3. Glad hands are:
securement devices.
warning devices.
coupling devices.
4. Which of the following is not a sign of fatigue?
Keeping a steady speed
Rubbing eyes
Frequent blinking
5. Air brakes:
are an effective way to stop large and heavy vehicles.
are prohibited on larger vehicles.
should be used only when driving on wet roads.
6. You should always try to back toward the driver's side because:
backing toward the left side is more dangerous.
you can watch the rear of your vehicle out the side window.
None of the above.
7. Drivers transporting cargo are responsible for:
inspecting the cargo.
recognizing overloads.
All of the above.
8. You are driving on a steep downgrade in the proper low gear. Your "safe" speed is 40 mph. When your speed reaches 40 mph, you should:
apply the brakes to quickly reduce your speed to 25 mph, and then release the brakes.
increase your speed to approximately 45 mph, and then apply release the brakes.
apply the brakes to gradually reduce your speed to 35 mph, and then release the brakes.
9. On dry pavement, the braking distance when traveling at 55 mph is about:
216 feet.
142 feet.
419 feet.
10. If your vehicle thumps or vibrates heavily, it may be a sign that:
you need to shift up.
the brakes have failed.
one of the tires has gone flat.
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IA CDL Doubles Triples Test

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