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 two, three or four answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the Nebraska 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. If using the spring brakes while hauling a heavy load, a complete stop will:
Explanation
Spring brakes will activate in a vehicle with air brakes if the pressure in the air system becomes too low. A heavily loaded vehicle will take a long time to stop when using only the spring brakes because the spring brakes do not work on all axles.
20. Before driving a vehicle with a dual air brake system, you must wait for the air compressor to build a minimum of ____ in both the primary and secondary systems.
Explanation
Before driving a vehicle with a dual air brake system, you should wait for the air compressor to build up at least 100 psi in both the primary and secondary systems.
21. 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.
22. When the brake pedal is pushed down, air brakes work:
Explanation
Because air takes time to flow through the air lines to the brakes, air brakes cannot begin working instantly. There is often a brake lag of at least one-half of a second between the moment the brake pedal is pressed and the moment the brakes begin to work.
23. 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.
24. If braking at a speed of 55 mph while driving on dry pavement, the brake lag can add ____ to your vehicle's total stopping distance.
Explanation
The total stopping distance for vehicles equipped with air brakes is made up of four factors: perception distance, reaction distance, brake lag distance, and braking distance. When braking at a speed of 55 mph while driving on dry pavement, the brake lag can add around 32 feet to a vehicle's total stopping distance.
25. ____ make up the emergency brake system.
Explanation
