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Iowa CDL Permit Test - Air Brakes

(From the 2020 Iowa CDL driver handbook)
Number of questions: 25
Passing score: 20
Directions: This endorsement is required for driving a vehicle with air brakes. To receive this endorsement, applicants must pass a written test. The test consists of 25 multiple choice questions. Each question has three answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the Iowa Commercial Driver License Manual. Questions come from the chapter covering: Air Brakes. The Air Brakes endorsement may be used with the Class A, B or C CDL.
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Passing grade —
5 or fewer errors
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1.
If you are driving and the ABS light comes on, it means that the ABS:
Cannot work due to weather conditions.
Has just been activated.
Is not working properly.
2.
To make a stop in a vehicle equipped with air brakes, the driver should:
Press the brake pedal down.
Lift the brake pedal up.
Pull out the air brake knob.
3.
In a dual air brake system:
Air tanks are shared between both systems.
Each system has its own air tanks.
You must designate which system you are using.
4.
If the low air pressure warning signal comes on in a vehicle with air brakes, the driver should:
Test the brakes while driving, but continue driving if nothing seems wrong.
Immediately stop driving.
Drive with the hazard lights activated.
5.
Brakes out of adjustment will:
Work properly.
Cause some of the brakes to overwork and malfunction.
Allow better acceleration.
6.
How much distance will an air brake-equipped vehicle need to come to a complete stop if it is traveling at 55 mph under ideal driving conditions?
300 feet
100 feet
450 feet
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