What is the minimum air pressure at which the low air-pressure warning device should activate?

The minimum air pressure at which the low air-pressure warning device should activate is correctly stated as 55 psi. This is an important safety feature in a vehicle equipped with air brakes, as it alerts the driver to a potentially unsafe condition when the air pressure falls below this threshold.

When the pressure drops to 55 psi, it indicates that the air system is nearing a critical point where the brakes may not operate effectively, creating a risk of brake failure. The low air-pressure warning is designed to provide an early warning to the driver, allowing for appropriate action to be taken before the brakes become inoperative.

Understanding this value is crucial for drivers as it ensures they maintain proper air pressure levels for safe operation of the vehicle. Monitoring the air pressure is essential to prevent accidents due to brake system failures, especially in commercial vehicles that rely heavily on air brakes.