Swiss fact: it is illegal to drive with your lights off during the day

Some cars have two sets of forward-facing lights: regular headlights and running lights. According to Swiss car club TCS, if your car has running lights these can be used during daylight hours. If it doesn’t you must use your regular headlights in the dipped position. Running lights are the horizontal strip of lights at the bottom of the light shown in the photograph below. Running lights are not sufficient in tunnels where main lights must be used.
Daytime light rules are stricter in Switzerland than neighbouring countries. In France and Austria, lights are required during the day if visibility is poor. In Germany, headlights must be used during daylight hours if fog, snow or rain restricts visibility. Italy is closer to Switzerland and requires lights during the day when driving outside of towns and when visibility is poor.
As a general rule, always driving with your main lights on will keep you out of trouble.