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 four answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the Colorado 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
19. During a static leakage test, the maximum leakage rate for a double combination vehicle is:
Explanation
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 air leaks from the air brake system at a quicker rate, the vehicle should not be driven because something likely needs to be repaired.
20. Front wheel braking works:
Explanation
Front wheel braking is effective under all road conditions. It is unlikely that you will experience a front wheel skid, even on ice.
21. The application pressure gauge:
Explanation
In an air brake system, the application pressure gauge shows how much air pressure is being applied to the brakes. Not all vehicles with an air brake system have this gauge.
22. If the spring brakes are activated, you should never:
Explanation
Never apply the brake pedal if your spring breaks are activated. Brakes can be damaged if they are subject to both springs and air pressure.
23. Which of the following is not a part of an air brake system?
Explanation
Air brakes consists of three separate braking systems: the service brake system, the parking brake system, and the emergency brake system.
24. In a vehicle with dual parking control valves, once air pressure is lost and the spring brakes come on:
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.
25. Air tank drains:
Explanation
