Normal Operating Procedures and Braking Technique
What the exam tests
This domain covers how to use air brakes in normal driving, especially on downgrades. The exam tests controlled braking, stab braking, gear selection, and the mistakes that cause fade or loss of control.
Before moving
Build air pressure to governor cut-out, check both gauges, confirm the warning system is off, release the parking brake only after pressure is adequate, and test the service brake at low speed.
Braking technique
Use controlled braking for normal stops: apply the brake firmly enough to slow the vehicle without locking the wheels, hold, and adjust as needed. Use stab braking in an emergency: apply fully, release when wheels lock, then reapply. On a long downgrade, select a lower gear before the grade, use engine braking, and make short, firm brake applications. Do not ride the brakes continuously; heat buildup causes fade.
Worked example
A loaded truck starts a 6% downgrade in a gear that is too high, and speed climbs. The correct response is to downshift before speed is too high, use the engine brake, and apply the service brakes in short snubs. Continuing to hold the pedal lightly will overheat the brakes.
Traps that cost marks
Do not coast in neutral or rely on the spring brake to stop. Do not fan the pedal repeatedly to control a downgrade. Do not assume air brakes react like hydraulic brakes; there is a lag. Do not use the trailer hand valve as a parking brake.