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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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Passing grade —
5 or fewer errors
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1.
What is brake lag?
The time required for the brakes to work after the brake pedal is pushed
The distance between the brake pedal’s resting position and the floor
The amount of air pressure used to stop a vehicle
How faded the brakes are
2.
If a vehicle has air brakes, the air compressor drive belt should be checked before each drive. In what condition should the belt be?
Loose
Tight
Cracked
Bumpy
3.
The air storage tanks:
Hold only enough air for one braking cycle.
Hold enough air for brakes to be used several times if the compressor stops working.
Do not hold air unless there is an emergency.
Hold enough air for more than 1,000 braking cycles.
4.
While driving, spring brakes are generally held in place by:
Air pressure.
Chocks.
Foundation brakes.
Sturdy ties.
5.
When the spring brakes are activated in a vehicle with air brakes, you should never:
Turn on the lights.
Turn the vehicle off.
Push the brake pedal down.
Open the trailer doors.
6.
Friction inside a brake drum is caused when the brake shoes and linings:
Push against each other.
Separate from the axle.
Push against the inside of the drum.
Create excess heat.
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