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 Idaho Commercial Driver’s License Manual l. 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. Failing to drain air tanks could result in:

Water accumulations freezing and causing brake failure.

Squishy brakes.

Too much air collecting in the tanks.

In an air brake system, the air tanks must be periodically drained to remove accumulations of water and compressor oil. If water is not removed, it could freeze in cold weather and cause brake failure.

20. What does the air compressor governor do?

It stops the compressor from pumping air.

It turns on the air compressor.

It stores the compressed air.

In an air brake system, the air compressor governor controls when the air compressor pumps air into the storage tanks. It stops pumping if the pressure in the tanks becomes too high, and begins pumping if the pressure becomes too low.

21. If the spring brakes are on, you should:

Not use the brake pedal.

Press the accelerator.

Move the steering wheel.

Do not use the brake pedal when the spring brakes are on. This could damage the brakes by subjecting them to the combined forces of springs and air pressure.

22. When stopping in an emergency situation, you should:

Veer your trailer to the right and stop.

Stop in a straight line.

Veer your trailer to the left and stop.

If you need to make an emergency stop, you can use either the controlled braking method or the stab braking method. It's important to brake in a way that keeps your vehicle in a straight line but will still allow you to turn if necessary.

23. When parked on a flat surface, you should:

Use wheel chocks to prevent your vehicle from moving.

Not use wheel chocks.

Use wheel chocks, but only if you have applied the parking brake.

When parking on a level surface, you should use wheel chocks. If the vehicle is not equipped with spring brakes, this is essential to prevent the trailer from moving.

24. During a static leakage test, what is the maximum leakage rate that is safe for a double combination vehicle?

3 psi in one minute.

6 psi in one minute.

8 psi in one minute.

When performing a static leakage test on a double combination vehicle with air brakes, the leakage rate should be no more than 3 psi in one minute. If the air leaks from the air brake system at a quicker rate, the vehicle should not be driven because something likely needs to be repaired.

25. How much distance will an air brake-equipped vehicle need to come to a complete stop if it is traveling at 55 mph under ideal driving conditions?

300 feet

100 feet

450 feet

A vehicle's total stopping distance is made up of perception distance, reaction distance, brake lag distance, and braking distance. With all of these factors included, an air brake-equipped vehicle traveling at a speed of 55 mph under ideal driving conditions will need approximately 450 feet to come to a complete stop.

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