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. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the Ohio Commercial Driver’s License Manual. Questions come from chapter covering: Air Brakes. The Air Brakes endorsement may be used with the Class A, B or C CDL.

Number of Question
Passing Score

19. If the low air pressure warning signal comes on in a vehicle with air brakes, the driver should:

Explanation
If the low air pressure warning signal comes on while you are operating a vehicle with air brakes, you should stop and safely park the vehicle as soon as possible. It is essential that you are able to stop safely while you still have some braking power remaining.

20. If an air compressor is belt-driven, the belt should be routinely checked to ensure that it is:

Explanation
If your vehicle has air brakes, the air compressor drive belt should be checked before each drive. Check the tightness of the belt and verify that it is in good condition.

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

Explanation
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.

22. A low air pressure warning signal should activate:

Explanation
In an air brake system, a low air pressure warning signal must come on if air pressure in the tanks falls below 60 psi. This warning signal may come in the form of a light, a buzzer, or a wig wag.

23. What helps prevent wheel lockup when braking?

Explanation
The purpose of an Anti-Lock Braking System (ABS) is to prevent wheel lockup while brakes are being applied.

24. If the safety relief valve in an air brake system is releasing air:

Explanation
The safety relief valve in an air brake system releases air if necessary to prevent pressure in the system from becoming too high. If the valve starts releasing air, there is something wrong. Have a mechanic fix the problem.

25. If air pressure drops to a level between ____, a visual low pressure warning signal should have already activated.

Explanation
A visual low pressure warning signal should activate before air pressure drops to a level between 55 and 75 psi. This signal could be a light, a buzzer, or a wig wag.
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