Normal Operating Procedures and Braking Technique
Normal Operating Procedures and Braking Technique
This domain tests how to use air brakes in everyday driving: pre-drive pressure, smooth application, downhill control, and parking. The exam favors the technique that keeps pressure up and brakes cool.
Core rules
- Before moving, build to governor cut-out, confirm the warning buzzer/light works, and check that the parking brake releases fully. Low pressure means stop; do not “drive it up” by revving the engine.
- Apply the foot valve progressively. Air brakes have lag, so look ahead and begin stopping earlier than in a hydraulic-brake car. Do not pump the treadle in normal stops; each application uses air and can leave you with less reserve.
- On long or steep downgrades, select a low enough gear before the grade and use snub braking: apply firm, steady pressure to reduce speed about 5–10 mph, release, let speed rebuild slightly, and repeat. Do not ride the brakes continuously; that overheats drums/rotors and causes fade.
- Use engine braking and proper gearing to control speed. Do not coast in neutral.
- When parking, set the parking brake, place the transmission in a low gear or park, and use wheel chocks when appropriate. Do not rely on air pressure alone to hold a parked vehicle.
Worked example
You are descending a long 6% grade with a loaded combination. At the top, choose a gear that holds a safe speed without service brakes, then use short snub applications to keep speed in check. If you instead hold light continuous pressure, heat builds, brake fade develops, and stopping distance grows. If pressure begins falling, stop and find the leak rather than continuing.
Traps
Do not use the parking brake as a normal service brake, and do not shift to neutral to save fuel on a downgrade. Do not “fan” the brakes to cool them; that wastes air.