In a school bus with a dual air brake system, what is the minimum allowed air loss when service brakes are applied?

In a school bus equipped with a dual air brake system, the minimum allowed air loss when the service brakes are applied is 3 psi over a one-minute period. Maintaining this standard is critical because it ensures that the air brake system remains functional and can effectively operate under pressure. An air loss greater than this threshold could indicate a leak or malfunction in the braking system, which poses a safety risk.

The specification of 3 psi is designed to ensure that there is enough air pressure to allow for reliable braking performance while still being indicative of the system's integrity. If the air loss exceeds this level, it is likely that the vehicle will need maintenance or inspection to identify and rectify possible issues. Understanding the operational range of the air brake system is essential for school bus drivers, as it directly correlates to the safety of the passengers they transport.