Air Brakes

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This endorsement is required for driving a vehicle with air brakes. To receive this endorsement, applicants must pass a written..

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

Passing grade:

When only the tractor is equipped with an Anti-Lock Braking System (ABS):

Explanation
If a tractor is equipped with an Anti-Lock Braking System (ABS) but the trailer is not, the risk of jackknifing will be reduced and the driver should still be able to maintain steering control. If only the trailer is equipped with ABS, it is less likely that the trailer will swing out to one side.

In cold weather, an alcohol evaporator should be checked and filled:

Explanation
An alcohol evaporator can help prevent ice from building up in an air brake system. In cold weather, the evaporator should be checked and refilled every day.

The service brake system:

Explanation
Air brakes consists of three separate braking systems: the service brake system, the parking brake system, and the emergency brake system. The service brake system applies and releases the brakes when you use the brake pedal while driving normally.

When leaving a vehicle unattended, a driver should:

Explanation
Always apply the parking brake when leaving your vehicle unattended.

Friction inside a brake drum is caused when the brake shoes and linings:

Explanation
Friction inside a brake drum is caused when the brake shoes and linings push against the inside of the drum. The friction in the drums will slow and stop the vehicle.

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.
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