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 or four answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the South Dakota 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. What can happen if a parking brake is used in very wet weather when temperatures are below freezing?

The brakes will squeak.

The brakes may freeze so the vehicle cannot move.

The brakes may suddenly release by themselves.

The brakes may explode.

If you use the parking brakes when the weather is very wet and the temperature is below freezing, the brakes may become frozen, preventing the vehicle from moving.

20. A vehicle equipped with an Anti-Lock Braking System (ABS) uses a ____ light to warn that the system is not working properly.

Green

Yellow

Orange

White

Anti-Lock Braking System (ABS) malfunction lamps are usually yellow. Even if the ABS isn't working properly, a driver will still have access to the vehicle's usual braking functions.

21. When the brake pedal is depressed, air brakes work:

Immediately.

After a short delay.

After about a minute.

Only if the green lever on the control panel is pushed down.

After the brake pedal is pushed down in a vehicle with air brakes, it takes a half-second or more for air to flow through the lines and make the brakes work. This contrasts with hydraulic brakes used in cars and light and medium trucks, which instantly begin working when the pedal is pushed.

22. You must have an air brake endorsement:

To use a vehicle with air brakes.

To drive any truck with a trailer.

To transport hazardous materials.

You must take an air brakes knowledge test to become licensed to operate a vehicle that is equipped with air brakes, including an air over hydraulic braking system.

23. Braking mechanisms are located ____ a brake drum.

Outside

Inside

Next to

On top of

Drum brakes are attached to the wheels and located on the axles of a vehicle. The braking mechanisms that cause the vehicle to stop can be found inside of a drum brake.

24. During an applied leakage test, the maximum leakage rate for a triple combination vehicle is:

10 psi in a minute.

8 psi in a minute.

6 psi in a minute.

4 psi in a minute.

It is important to know the maximum air loss rate that is safe for your specific vehicle. A triple combination should have a leakage rate no higher than 6 psi in a minute during an applied leakage test.

25. Why should you regularly drain the air tanks?

Because the air gets old and needs to be replaced

Because compressed air contains some water and the water collects in the tanks

To allow for a change in pressure

Compressed air usually contains a certain amount of moisture and compressor oil, which can build up in the air storage tanks and damage the brake system. The tanks should be drained to clean out these accumulations. On a tank with a manual drain valve, draining should be performed at the end of each day of driving.

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