When are headlights required to be turned on in Missouri?

Headlights are required in Missouri from sunset to sunrise, and when visibility is less than 500 feet due to conditions such as rain, fog, or snow. This regulation ensures that drivers can see the road clearly and be seen by other motorists, which enhances safety during low-light and low-visibility situations. The requirement during specific visibility conditions helps to mitigate the increased risk of accidents when environmental factors hinder clear sight.

The other options do not encompass the full scope of when headlights must be used. For instance, headlights are not limited to just heavy rain or fog; they are also essential when it is dark outside. Likewise, while some may suggest headlights should be on all the time, Missouri law specifies certain conditions rather than a blanket requirement at all times. Finally, the time frame of 6 PM to 6 AM does not account for seasonal changes in daylight hours, making it an incomplete guideline. Therefore, the correct response is that headlights must be used during nighttime and poor visibility conditions, which is clearly outlined in option A.