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Iowa CDL Permit Test - Air Brakes

(From the 2019 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.
You have made error so far
Passing grade —
5 or fewer errors
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1.
Alcohol evaporators are:
Illegal.
Used to add alcohol to braking systems to prevent items from freezing.
Only allowed on vehicles carrying hazardous materials.
2.
What do air brakes use to make the brakes work?
Compressed air
Outside air
Non-compressed air
3.
If the safety relief valve in the air brake system releases air:
The compressor needs more air.
The air pressure has become too high.
The brakes are fully operational.
4.
ABS brakes:
Help you avoid wheel lockup.
Lock up your vehicle's wheels.
Prevent your vehicle from accelerating when going uphill.
5.
On flat surfaces, wheel chocks:
Can be used to prevent a parked vehicle from moving.
Make it easier for a parked vehicle to roll.
Should only be used on the front driver's side tire.
6.
Foundation brakes are used:
Only on the front wheels of a vehicle.
Only on the rear wheels of a vehicle.
On each wheel of a vehicle.
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