One of the most important safety features of your vehicle is your headlights. They ensure that you can see and that other drivers can see you. Headlights are required to be on from sunset to sunrise, due to insufficient light. Also headlights are turned on during unfavorable atmospheric conditions such as rain, mist, fog or poor visibility.
Some mountainous roads and other narrow winding roads in difficult terrain have signboards mentioning to turn on your headlights due to poor visibility. Anytime you have trouble seeing the road in front of you or seeing other cars, it means you have to use the headlights. Your headlights will help you avoid a head-on crash.
You also have to use your headlights wisely. Do not blind other drivers with your high beam headlights. You need to switch to low beam based on the distance of the vehicle coming in front of you and similarly if you are driving behind another vehicle.