What is the purpose of the warning buzzer in an air brake system?

The purpose of the warning buzzer in an air brake system is to alert the driver of low air pressure or a malfunction. This feature is crucial for ensuring the safe operation of the vehicle. In air brake systems, maintaining adequate air pressure is essential for effective braking performance. The buzzer serves as an early warning system that informs the driver when air pressure falls below a safe threshold, which could lead to brake failure if not addressed promptly. This allows the driver to take appropriate action, such as stopping the vehicle safely to prevent a dangerous situation.

In contrast, the other options do not accurately describe the primary function of the warning buzzer. The indication of engaged brakes, the signaling for brake pad replacement, and notifications regarding gear shifting are not the intended purposes of this warning system. Therefore, recognizing the correct function of the warning buzzer is key to understanding the importance of air pressure in maintaining overall braking effectiveness and safety on the road.