If a bus is equipped with a strobe light, when should it be activated based on visibility conditions?

The correct answer reflects the standard practice for school buses equipped with strobe lights, which are designed to enhance visibility in low-light or adverse weather conditions. Activating the strobe light when visibility falls to 500 feet or less is critical to ensuring that other drivers can see the bus from a distance, therefore promoting the safety of students boarding or disembarking.

When visibility drops to this threshold, such as during fog, heavy rain, or nighttime conditions, the strobe light serves as an important safety measure. It helps alert other motorists to the presence of the school bus, thereby reducing the likelihood of accidents. This is especially crucial in areas where children are crossing the street near schools or bus stops.

Other visibility conditions listed in the options entail distances greater than 500 feet, which may not effectively signal the presence of the bus in time to prevent potential hazards. Thus, activating the strobe light at this specified distance strikes an essential balance between safety and practical visibility standards for school buses.