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Iowa CDL Practice Test: Double and Triples - Test 3 2020

(From the 2020 Iowa CDL Handbook)
Number of tests: 26
Number of questions: 30
Passing score: 80

Directions: To obtain this endorsement for pulling two or three trailers, applicants must pass a 15-question test. And to pass the test, applicants must score at least 80%. Test questions are from the Iowa Commercial Driver Handbook. The Double/Triple trailers endorsement can be used with the Class A CDL. If you need additional information, please contact your local DMV office. You can find your nearest DMV office at Iowa DMV locations.

1. The pressure in the service line indicates ______.

2. When you are backing up with a trailer what should you do first?

3. The spring brakes come on when the air pressure drops into what range _________.

4. Usually, a fully charged air system has _______ psi.

5. What are hose couplers?

6. Which of the following is a necessary step to ensure that you have the best control of your double or triple on a curve?

7. Trailers that do not have spring brakes have emergency brakes, which work from ________.

8. The tractor protection valve ______.

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