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. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the Ohio Commercial Driver’s License Manual. Questions come from chapter covering: Air Brakes. The Air Brakes endorsement may be used with the Class A, B or C CDL.
Number of Question
Passing Score
7. When parking, you should not use the parking brake if:
Explanation
If your brakes are hot after coming down a steep grade, you should not use your parking brake when parking. Let your brakes cool before applying the parking brake or risk damaging the brakes.
8. Failing to drain air tanks could result in:
Explanation
In an air brake system, the air tanks must be periodically drained to remove accumulations of water and compressor oil. If water is not removed, it could freeze in cold weather and cause brake failure.
9. Having ABS on only one axle:
Explanation
If you have an Anti-Lock Braking System (ABS) equipped on only the tractor, only the trailer, or only one axle, you will still have more control over the vehicle when braking than you would without ABS. You should brake normally.
10. Once the air tanks are at an air pressure level of 125 psi, the air compressor governor will:
Explanation
An air compressor governor will stop the compressor from pumping air once the air tanks are at an air pressure level around 125 psi. This air pressure level is referred to as the "cut-out" level.
11. Brake linings should be:
Explanation
Brake linings should not be loose or soaked with oil or grease. They shouldn't be dangerously thin.
12. If the safety relief valve in the air brake system releases air:
Explanation
