Instructions

Air Brakes

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.. Read More

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.

Number of Question 25

Passing Score 20

19. Emergency brakes:

Are not required on trucks.

Are only required on trailers.

Are required on tractors.

Are optional.

All trucks, truck tractors, and buses must be equipped with emergency brakes and parking brakes. These brakes must be held by mechanical force.

20. Spring brakes come on:

When too much air pressure is lost.

When a control on the dashboard is activated.

When the tires have minimal tread depth.

When the brakes are noisy.

Spring brakes come on automatically when air pressure drops to an unsafe psi level. Instead of waiting for the spring brakes to automatically activate, you should safely exit the road as soon as you notice the low pressure warning signal and bring your vehicle to a stop while you are still able to control the brakes.

21. Some air brake systems use alcohol:

To reduce the risk of ice forming in air brake valves.

To make the compressor run more efficiently.

To lubricate parts of the braking system.

To reduce the risk of rust forming on air brake valves.

Some air brake systems contain an alcohol evaporator. This device introduces alcohol into the braking system to inhibit the formation of ice.

22. To stop in a vehicle that uses air brakes, the driver should:

Pull the air brake lever.

Engage the brake lever.

Push the brake pedal down.

Pull the brake pedal up.

To make a normal stop in a vehicle with air brakes, push the brake pedal down. The harder the pedal is pressed, the more air pressure is released.

23. You should not use the parking brake:

If your vehicle is stopped on a level surface.

If your vehicle is stopped on a slight incline.

If your vehicle's brakes are very hot.

If your vehicle's other braking systems seem to be working adequately.

A parking brake should not be used if the vehicle's brakes are very hot from use on a steep downgrade or if the brakes are very wet and temperatures are freezing. Using the parking brake when brakes are hot could cause damage to the brakes, and using the brakes when they are wet in freezing weather may cause the brakes to ice up, rendering the vehicle immobile.

24. Test the low pressure warning signal:

Once a month.

Once a week.

Twice a week.

Before every trip.

It is essential that your low pressure warning light function properly. After allowing the system to charge, you can test the warning signal by rapidly applying and releasing the brake pedal. This will release air from the braking system and the warning signal should come on when pressure drops to a dangerous level.

25. Vehicles with dual air brake systems:

Maintain full-capacity air pressure in the braking systems even when the vehicle is not running.

Maintain some air pressure in the braking systems when the vehicle is not running.

Must be run to build enough air pressure to brakes to operate properly.

Do not need time to build air pressure before a trip.

Before driving a vehicle with a dual air brake system, you must allow the air compressor time to build up at least 100 psi of air pressure in both the primary and secondary systems.

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