What is the functionality of the acoustic sensors on the 3000 series buses?

The correct answer indicates that the acoustic sensors on the 3000 series buses are designed to enhance safety by preventing the front and rear doors from closing if an obstruction is detected. This functionality is crucial as it helps to protect passengers from injury and ensures safe boarding and alighting.

These sensors work by detecting any object or person that could be in the path of the closing doors. If the sensors recognize an obstacle, they trigger a mechanism that stops the doors from closing, allowing individuals to either step out of the way or board safely. This design reflects a commitment to passenger safety and aligns with best practices in public transportation.

In contrast, the other options do not accurately describe the role of the acoustic sensors. For instance, signaling the driver to speed up would not relate to door safety, while monitoring bus speed does not pertain to the functionality of the sensors themselves. Similarly, alerting pedestrians is an important aspect of bus operation but is not the primary function of acoustic sensors, which are specifically designed for door safety.