What is indicated when the parking brake is fully engaged?

When the parking brake is fully engaged, it indicates that air pressure is at safe levels. This is important because many school buses use an air brake system, which relies on compressed air to operate effectively and safely. A fully engaged parking brake signals that the air pressure has stabilized and is sufficient for the brake system to function correctly.

In the context of school bus safety, ensuring that air pressure is at safe levels is crucial before operating the vehicle. If air pressure were insufficient, it could lead to brake failure, posing significant risks to both passengers and other road users. Therefore, confirming that air pressure is adequate is a key part of pre-trip inspections and maintaining safe operating conditions for the bus.