What is the appropriate air pressure range for the parking brake button to pop out?

The appropriate air pressure range for the parking brake button to pop out is 20-45 psi. This range is crucial for the reliable functioning of the air brake system in a school bus.

When the air pressure in the system drops below a certain threshold, the parking brake is designed to engage automatically, preventing the bus from rolling away. The specified range ensures that there is sufficient air pressure to keep the brake released during normal operation, while still allowing for a failsafe mechanism that engages the parking brake when air pressure gets too low.

Maintaining air pressure within this range is critical for ensuring both the safety of the bus and its passengers. If the pressure is too low, it can indicate a problem with the air brake system, necessitating immediate attention from maintenance personnel. The pressure range helps drivers be aware of the health of the braking system and act accordingly.