When is it necessary to use headlights during the day in Delaware?

The correct answer highlights a safety requirement regarding visibility. In Delaware, using headlights during the day is necessary only when visibility is less than 1,000 feet. This is an essential rule, as it ensures that vehicles are visible to other drivers and pedestrians in conditions such as fog, rain, or heavy snow. By requiring headlights under these circumstances, Delaware aims to reduce accidents that might occur due to insufficient visibility.

The other options present scenarios where headlights may be useful but do not align with the specific legal requirement outlined. For example, while driving on highways might call for additional visibility, it does not mandate the use of headlights unless visibility drops below the defined threshold. Similarly, during bad weather, the use of headlights is critical, but this requirement is tied to visibility rather than the weather itself. Lastly, headlights being necessary only at night would neglect the crucial function they play in enhancing safety during daytime conditions with poor visibility.