OR CDL Air Brakes study guide
OR CDL Air Brakes · Work through your exam, one topic at a time.
The Oregon CDL Air Brakes Knowledge Test is the written endorsement exam a commercial driver must pass before operating a vehicle equipped with air brakes. Oregon requires the air brakes restriction to be removed from a CDL before a driver may legally operate air-brake-equipped trucks, buses, and combinations, so this test matters for anyone moving into heavy vehicles, school buses, or tractor-trailer work. The OR CDL Air Brakes study guide has 6 sections and about 1,814 words.
01Air Brake System Components and Function
This domain tests how an air brake system produces, stores, controls, and applies compressed air to stop a vehicle. Oregon CDL questions focus on the compressor, governor, reservoirs, valves, brake chambers, slack adjusters, and foundation brakes - and on what each part does, not just its name.
320 words, about 2 min02Dual Air Brake System and Safety Features
This domain tests the dual air brake system: two separate circuits, warning and protection devices, and the safety features that keep one failure from causing total brake loss. Most modern systems split into primary and secondary circuits.
325 words, about 2 min03Inspecting the Air Brake System
This domain tests the pre-trip inspection sequence for air brakes: building pressure, checking compressor cut-in and cut-out, leakage, warning devices, spring brakes, and the mechanical condition of chambers, slack adjusters, and lines. Start with a fully charged system and wheels chocked.
289 words, about 1 min04Air Brake System Checks (Leakage, Low Pressure Warning, Spring Brakes)
This domain tests the specific pass/fail air brake checks: leakage, low-pressure warning, spring brake operation, and compressor buildup. The exam wants numerical limits and correct test conditions.
292 words, about 1 min05Using Air Brakes While Driving
This domain tests how to use air brakes while driving: recognizing lag, controlling speed on grades, avoiding fade, and choosing the right brake controls. Air brakes have lag.
286 words, about 1 min06Emergency Braking and Brake Failure Response
This domain tests emergency braking and brake failure response: low pressure, partial circuit failure, spring brake application, fade, and runaway situations. If the low-pressure warning sounds, stop safely as soon as possible; do not try to reach a repair shop.
302 words, about 2 min