When must drivers use headlights according to visibility conditions?

Drivers must use headlights when visibility is less than 500 feet. This regulation ensures that drivers can see clearly and be seen by others, enhancing safety on the road, especially during conditions such as fog, rain, or night driving when distance visibility is reduced. By using headlights under these circumstances, drivers can improve their ability to spot obstacles, other vehicles, and road signs while also ensuring that other motorists are aware of their presence.

In contrast, the other options suggest different visibility distances that are not in line with the requirements outlined by the Indiana driving regulations. Proper headlight use is critical for safe driving, particularly when visibility falls below the specified threshold.