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District Of Columbia CDL Permit Test - Air Brakes

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 four answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the Washington D.C. 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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5 or fewer errors
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1.
When about to drive a vehicle with a dual brake system, a driver should:
Let the vehicle warm up to ensure the fuel reaches the engine.
Wait for air pressure to build in both the primary and secondary systems.
Begin driving just after the engine starts.
Pump the pedal about 20 times to build pressure, then begin driving.
2.
In a dual air brake system:
Each system has separate air tanks, hoses, and lines.
The systems share air tanks, but each has its own separate hoses and lines.
Each system uses the same lines and hoses.
One system is the main braking system and a second system is ready to be used if the first one fails.
3.
Service brakes should:
Be tested once a month.
Only be tested by a trained mechanic.
Be tested before every trip.
4.
An Anti-Lock Braking System (ABS):
Cannot be used with air brakes.
Should be used on dry pavement.
Can assist in maintaining control when braking.
Should only be used if all axles have ABS.
5.
What must be on an air tank in an air-braked vehicle?
A check valve
A lock
A trap door
An oxidizer
6.
What does the air compressor governor do?
Controls when the air compressor pumps air into the air storage tanks.
Controls how quickly air leaves the air storage tanks.
Controls the temperature of the air entering the air storage tanks.
Controls the temperature of the air leaving the air storage tanks.
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