What visual or auditory signal indicates low air pressure in a vehicle's braking system?

A low air pressure alarm and light is the correct indication of low air pressure in a vehicle's braking system. This system is critical for the safety and functionality of the braking system in commercial vehicles, which often rely on air brakes. The low air pressure alarm serves as a direct warning to the driver that the air pressure has fallen to a level that could compromise the effectiveness of the brakes. It is designed to help maintain awareness of the vehicle's operating condition, allowing the driver to take necessary actions before the pressure drops too low and affects braking performance.

Other signals, such as a steady beep sound, flashing headlights, or a warning message on the dashboard may be relevant in different contexts, but none are specifically tailored to communicate the low air pressure situation as effectively as the alarm and light designated for that purpose.