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 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 25

Passing Score 20

1. When you are about to start down a hill, you should switch into a ____ gear.

Higher

Faster

Lower

Before starting down a hill, be sure to switch into a low gear. Gravity will increase your vehicle's speed as you travel downhill.

2. A safety valve is set to open at ____ pounds per square inch (psi).

100

150

200

The safety valve protects air tanks and the rest of an air brake system from accumulating too much air pressure. The safety valve is usually set to open at 150 psi.

3. When traveling down a steep downgrade:

The air brakes should be used.

The vehicle should be placed in a low gear and the driver should use engine braking.

The driver should continually downshift instead of using the brakes.

On long and/or steep downgrades, you should primarily use engine braking to control the speed of your vehicle. Use your brakes only as a supplement to this effect.

4. An alcohol evaporator in an air brake system:

Makes the brakes work without squeaking.

Prevents ice from forming in the braking system.

Lubricates parts of the braking system.

Some air brake systems include an evaporator that introduces alcohol into the system. The alcohol can help prevent ice from forming within the system.

5. A dual air brake system:

Consists of two separate air brake systems that share a single set of controls.

Is a single air brake system with two different sets of controls.

Consists of one air brake system for the left side of the truck and one system for the right side of the truck, each with its own set of controls.

A dual air brake system is made up of two separate air brake systems. The systems share a single set of brake controls, but each has its own air tanks, hoses, and lines. One system typically operates the regular brakes on the rear axle or axles while the other system operates the regular brakes on the front axle.