Most commercial vehicles utilize an air brake system over the traditional hydraulic brake system of passenger cars due to the "unlimited" supply the included air compressor and storage tanks can create. This eliminates the need to add hydraulic fluid when connecting a trailer.
The air brakes test covers the air brake system in detail, including appropriate air loss, brake lag, system components, and more. There are a total of 25 multiple choice questions on the air brakes exam, and you must score 80% (20 out of 25) to pass the exam. We have complied 100 questions you will find on the air brakes exam. These questions are based off the 2025 Tennessee CDL drivers’ manual.
The air brakes exam is different than the other endorsement tests, it actually serves as a restriction on your license. You are able to get a CDL without the air brakes test but will not be allowed to drive any vehicle that is equipped with air brakes because your license will have a "L" restriction.