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 questions. Each question has three answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the Oklahoma 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
Passing Score
13. Some water and compressor oil is usually found in the compressed air within an air brake system. The water and compressor oil:
Explanation
If water and compressor oil are left to build up in an air brake system, the system can be damaged. Air storage tanks are equipped with drains to allow this accumulation to be removed. Manually controlled drains should be operated at the end of each day of driving.
14. Brake fade is a result of:
Explanation
If brakes are overused, they can become too hot. This overheating causes them to fade, making them less effective at slowing the vehicle.
15. In a vehicle with dual parking control valves, a separate air tank can be used:
Explanation
In a vehicle with dual parking control valves, there is a separate air tank that can be used to temporarily release the spring brakes if they have been activated due to low air pressure. Pushing in the proper control will release the spring brakes for a short period of time, allowing the driver to move the vehicle in an emergency.
16. Air storage tanks:
Explanation
In an air brake system, the air storage tanks hold compressed air to be used by the brakes. The number and size of air tanks varies among vehicles.
17. Foundation brakes are used:
Explanation
Foundation brakes are used on each wheel of a CMV. The most common type of foundation brake is the s-cam drum brake.
18. Lights that indicate that anti-lock brakes are not working are:
Explanation
