What might occur if the air pressure drops below the specified range?

When the air pressure in the braking system of a school bus drops below the specified range, it can lead to the activation of the parking brake indicator light. This light serves as a crucial warning for the driver, indicating that the air pressure is not adequate to safely operate the braking system.

The parking brake system, particularly in air brake-equipped vehicles, relies on sufficient air pressure to keep the parking brake disengaged. If the air pressure falls too low, it may trigger the indicator light to alert the driver of the situation, allowing them to take necessary actions to ensure safety, such as pulling over to assess and address the problem before continuing to drive.

Inadequate air pressure compromises the braking system's effectiveness, posing significant safety risks. This is why the indicator light is an essential feature, highlighting any critical issues with the air braking system before they escalate further.