At what pressure must the low air warning device activate in a dual air brake system?

• A. 50 psi
• B. 60 psi
• C. 70 psi
• D. 80 psi

Answer: (B)

The correct answer is 60 psi because in a dual air brake system, the low air warning device is designed to activate when the air pressure drops to a critical level that could compromise braking safety. The standard threshold for this alert in commercial vehicles, including school buses, is set at 60 psi. This ensures that the driver is made aware of the low air pressure condition while there is still sufficient air pressure to control the vehicle safely.

Activating at this level allows the driver to respond promptly and take necessary actions, such as safely stopping the vehicle or addressing the air pressure issue before losing brake effectiveness. Recognizing this critical pressure helps maintain safety standards and ensures that the vehicle can be monitored effectively for operational integrity.