https://www.natlawreview.com/article/permanent-headlight-usage-shown-to-reduce-car-accidents:

> Even though headlights are most effective at night and during inclement weather, research is showing that they do make vehicles more visible to other motorists during a clear day as well. While each study varies, some have noted that headlight use during the day has resulted in a reduction of accidents by up to 10%. The types of accidents which were prevented were more significant, however.