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A valve that keeps air in the brake system should a bad leak occur
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A valve that prevents the trailer from being accidentally released
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A valve that prevents the vehicle from going too fast
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Iowa CDL Permit Test - Combination
(From the 2021 Iowa CDL driver handbook)
| Number of questions: | 20 |
| Passing score: | 16 |
Directions:
All applicants who are applying for a Class A CDL should be prepared to take the Combination test. This test covers information found in Section 6 of the Commercial Driver License Manual. Section 6 provides the information needed to safely operate tractor-trailers, doubles, triples, and straight trucks with trailers. The test is made up of 20 multiple-choice questions, and applicants will need to correctly answer a minimum of 16 questions to pass. The Combination test is not a replacement for the Double/Triple endorsement test.
Passing grade —
4 or fewer errors
advertising
1.
What is the tractor protection valve?
2.
When coupling a trailer:
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Make sure to couple the proper glad hands.
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Glad hands can be connected to any other glad hands.
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Only one set of glad hands should be connected.
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3.
If a trailer begins to jackknife, the driver:
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Should not apply the trailer hand brake.
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Should firmly apply the brakes.
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Can straighten the trailer with the parking brake.
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4.
In a vehicle equipped with an automatic tractor protection valve, the valve will pop out when air pressure drops to a level between:
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20 and 45 psi.
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75 and 105 psi.
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50 and 65 psi.
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5.
Before a trip, you can make sure air flows to all trailers by:
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Checking for moving air inside of each trailer.
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Listening for air at the rear shut-off valve.
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Feeling for air at the front shut-off valve.
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6.
When backing up your tractor while coupling it to a trailer, the trailer brakes should be:
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Deactivated.
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Locked.
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Unlocked.
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7.
To prevent a rollover, cargo should be:
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Loaded with most weight on the driver’s side of the trailer.
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Placed near the rear of the trailer.
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Spread out in the trailer.
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