What safety feature must be inactive when a school bus is transporting non-pupil passengers?

When a school bus is transporting non-pupil passengers, the stop signs must be inactive. This is because the stop signs are specifically designed to ensure the safety of pupils while they are boarding or disembarking from the bus. When the bus operates without transporting students, the stop signs are not needed as there are no children present who require protection during these moments.

The flashing red lights, emergency exits, and door alarms are safety features that serve different purposes. Flashing red lights alert other drivers that the bus is actively picking up or dropping off children, and emergency exits are crucial for evacuating passengers in case of an emergency, regardless of whether those passengers are pupils or non-pupils. Door alarms are safety mechanisms that help ensure that the doors of the bus do not open while the vehicle is in motion, further protecting all passengers on board. Therefore, the functionality of the stop signs is directly tied to the presence of students, making their inactivity when non-pupil passengers are on board the correct response.