Normal Operating Procedures and Braking Technique
Domain 5 covers normal driving with air brakes: preparing the system, applying the brakes smoothly, controlling speed on grades, and using parking and emergency brakes correctly. The Georgia CDL test rewards technique that preserves air pressure and brake temperature.
Operating rules
- Before moving, pressure must be at normal operating range, warning devices must work, and spring brakes must release fully. Monitor both supply and application gauges.
- Apply the treadle valve with steady pressure and release to release. Do not fan or pump the brakes; each application uses air and can drop pressure. Use engine braking and a lower gear before a downgrade.
- Do not ride the brakes. Continuous light application overheats drums and causes fade. Brake firmly enough to slow, then release or reduce pressure. At 55 mph, air brake lag adds distance; increase following distance.
- For parking, use the parking or spring brake and chock wheels when needed. Do not use the trailer hand valve for parking. Do not use spring brakes for routine stopping except in an emergency.
Worked example
On a long downgrade, a driver selects a lower gear before the grade and uses the engine brake. When speed rises, the driver applies the service brake firmly, then releases it rather than riding it. If the gauge begins to fall, the driver stops at a safe pullout and lets the system rebuild. Fanning the brakes would waste air and reduce control; staying in a high gear would rely too much on the brakes.
Traps that cost marks
Coasting in neutral, riding the treadle, and fanning are common failures. Another is using the parking brake to slow a moving vehicle; that can damage the spring brake. Do not assume air brakes apply instantly; lag is real. Do not ignore a falling gauge because the vehicle still stops once.
Key points
- Build full pressure and confirm spring brakes release before moving.
- Use steady brake pressure; do not fan or ride the brakes.
- Select a lower gear before a downgrade.
- Air brake lag increases stopping distance.
- Use the parking or spring brake for parking, not routine stopping.