In an air brake system, the low pressure warning light and buzzer must activate at all pressures of _______ or below

• A. 40 Psi
• B. 60 Psi
• C. 20 Psi
• D. 50 Psi

Answer: (B)

Air brake systems rely on stored compressed air to apply and release the brakes, and a warning light plus buzzer are used to alert the driver before pressure gets too low to brake reliably. The low-pressure warning is set to activate at 60 psi or below, which gives you enough time to react while there is still ample air in the system to maintain control and brake function. If pressure falls further, the system will eventually reach a point where more severe actions, like spring brakes engaging, could occur, but the warning is intentionally triggered at 60 psi to prompt timely action. That makes 60 psi the correct threshold.