When must you use headlights?

Using headlights is essential for ensuring visibility and safety while driving, both for the driver and other road users. The requirement to use headlights from sunset to sunrise is rooted in the fact that reduced daylight conditions significantly impair visibility. Additionally, they must be used in low visibility conditions, such as during heavy rain, fog, or snowfall. In such situations, headlights help illuminate the road and improve the driver's ability to see obstacles, but they also make the vehicle more visible to other drivers, enhancing overall safety on the road.

The other options do not account for all scenarios where headlights are necessary, such as driving in low visibility conditions not exclusively tied to nighttime driving. Hence, the comprehensive requirement stated in the correct response encompasses both time-based usage and conditions that hinder visibility beyond mere darkness.