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 four answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the 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 25

Passing Score 20

13. In a vehicle with dual air brakes, what happens if one system is low on pressure?

The air from the other system will be used to supplement the system with the low pressure.

The front or rear brakes may not work properly.

All brakes will be inoperable.

The low system will use an auxiliary system to fill the tank.

In a dual air brake system, if one of the air systems gets very low on pressure, either the front or rear brakes will not be operating fully. You should bring your vehicle to a safe stop and have the air system repaired.

14. In a dual air brake system:

Air tanks are shared by both systems.

Each system has its own air tanks.

You must designate which system you are using.

Brakes on only one side of the vehicle will work.

Most heavy-duty vehicles use dual air brake systems. A dual air brake system consists of two separate air brake systems, connected by a single set of brake controls. Each system has its own air tanks.

15. Emergency brakes:

Are not required on trucks.

Are only required on trailers.

Are required on tractors.

Are optional.

All trucks, truck tractors, and buses must be equipped with emergency brakes and parking brakes. These brakes must be held by mechanical force.

16. To ensure normal stopping power, drivers of vehicles equipped with a front brake limiting valve should:

Set the control to normal.

Set the control to the off position.

Set the control to neutral.

Keep the control at the halfway mark.

Some pre-1975 vehicles have a front brake limiting valve, which has "normal" and "slippery" settings. The idea behind these valves was to limit the air pressure available to the front brakes when driving on slippery surfaces, and thereby reduce the danger of a front-wheel skid. Studies have found that this is not actually a concern, so if your vehicle has a front brake limiting valve, leave it in the "normal" position.

17. Do not use the parking brake when parking if:

The brakes are very hot.

The brakes are very cold.

There is snow on the ground.

There is water on the ground.

A parking brake should not be used if the vehicle's brakes are very hot from use on a steep downgrade or if the brakes are very wet and temperatures are freezing. Using the parking brake when brakes are hot could cause damage to the brakes, and using the brakes when they are wet in freezing weather may cause the brakes to ice up, rendering the vehicle immobile.

18. 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.

25 psi

50 psi

75 psi

100 psi

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.

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