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 three answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the Louisiana 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. Alcohol evaporators are:

Illegal.

Used to add alcohol to braking systems to prevent items from freezing.

Only allowed on vehicles carrying hazardous materials.

Some air brake systems include an alcohol evaporator. The evaporator introduces alcohol into the braking system to prevent the formation of ice, which can cause damage.

20. You should ____ if the low pressure warning signal activates while you are driving.

Stop where you are and park

Exit the roadway as soon as safely possible

Continue driving normally

If the low pressure warning signal activates while you are driving, it is important that you safely exit the roadway as soon as possible and park your vehicle. If the air pressure gets too low, the brakes will no longer work well enough for you to stop safely.

21. An Anti-Lock Braking System (ABS):

Is not available for vehicles with air brakes.

Is not helpful in most driving situations.

Can help you maintain control when braking.

Anti-Lock Braking Systems (ABS) are compatible with air brakes and help a driver maintain control of their vehicle by preventing wheel lockup.

22. A wig wag is:

A low pressure warning device.

A tube that carries air to the brakes.

A type of air brake system.

Vehicles with air brakes are required to be equipped with a low pressure warning device. A wig wag is a type of low air pressure warning device. This device drops a mechanical arm into the driver's view if the pressure in the tanks drops to a level between 55 and 75 psi.

23. When an S-cam turns inside a brake drum, the S-cam:

Presses the brake shoes against the inside of the brake drum.

Presses the brake shoes against the brake linings.

Presses the brake linings against the wheel axles.

When a brake pedal is pressed and the S-cam is turned, the S-cam presses the brake shoes against the inside of the brake drum. This causes friction and will cause the vehicle to slow.

24. What is brake lag?

The time required for the brakes to work after the brake pedal is pressed

The distance between the brake pedal and the floor

The amount of air pressure used to stop the vehicle

Because air takes time to flow through the air lines to the brakes, air brakes cannot begin working instantly. There is often a brake lag of at least one-half of a second between the moment the brake pedal is pressed and the moment the brakes begin to work.

25. What tells you how much pressure is in your vehicle's air tanks?

The supply pressure gauge

The ABS malfunction lamp

The tractor protection valve

A vehicle that is equipped with air brakes must also be equipped with a supply pressure gauge. This gauge tells the driver how much air pressure is in each of the vehicle's air tanks.

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