When is it required to stop your vehicle for a school bus?

Answer: B — When the bus has its stop arm extended and lights flashing

Stopping for a school bus is mandated primarily when the bus has its stop arm extended and the lights are flashing. This is a crucial safety measure to protect children as they board or disembark from the bus. The visual cues of the stop arm and flashing lights serve as a clear indication that children may be crossing the street, and drivers must take immediate action to stop their vehicles to ensure their safety. In this context, the other options do not adequately reflect the law surrounding school buses. For instance, a bus having its turn signal on does not necessarily indicate that it is stopping to pick up or drop off children, nor does it require drivers to halt. Similarly, stopping only if children are crossing the street does not account for the importance of stopping for the bus itself, which is the primary concern. The idea that a driver should never stop unless directed by a police officer is incorrect; all drivers are required to abide by the traffic laws regarding school buses at all times. These regulations are in place to maximize safety for children and ensure an orderly traffic flow in school zones.