Parking Brakes and Safe Parking
The Parking Brakes and Safe Parking domain combines the mechanics of the parking brake with judgment about grades, chocks, and wheel position.
Rules for a safe park
- Apply the parking brake fully - the yellow knob pulled out. Spring brakes are mechanical, so they hold even if air leaks away.
- Put the transmission in the lowest gear, or park. Never leave it in neutral.
- Chock the wheels whenever the vehicle could roll.
- Turn the front wheels toward the curb when facing downhill, and away from the curb when facing uphill with a curb.
- With no curb, turn the wheels so a roll would take the vehicle off the road, not into traffic.
- Never use the parking brake as a service brake to stop. It applies only the rear wheels and can cause a jackknife or loss of steering control.
What actually holds the truck
During normal driving, air pressure keeps the spring brakes released. When you park, you dump that air, and the vehicle then depends on the spring, the gear, and the chocks.
Worked example
A driver parks a loaded tractor-trailer facing downhill on a street with a curb. Correct setup: parking brake applied, transmission in low gear, front wheels turned into the curb, chocks placed if available. Leaving the wheels straight, or turning them away from the curb, is the classic wrong answer.
Traps
Turning the wheels the same way on every slope; forgetting that "away from the curb" applies only when facing uphill; parking with the brake only partly set; relying on residual air pressure instead of the mechanical spring.