We have all noticed the large number of car owners who drive through tunnels, during the twilight hours – and even at night – with solely their daytime running lights on. Such situations undoubtedly demand more illumination than these lights are capable of providing, and the drivers of said vehicles are also risking a fine. On some occasions, when snow if falling, for example, daytime running lights are not even the best option during daylight hours.
But why should we be reaching for the light switch to turn our low-beam headlights on? In snowy conditions, the situation is clear-cut: reduced visibility alone means we need more illumination than our daytime running lights can give us. Don’t forget that the rear lights of many vehicles only come on together with the headlights! A further problem is the tendency for daytime running lights to become obscured by falling snow, with a resulting dramatic decrease in brightness. This particularly applies to models that are physically separate from the headlights and mounted low down on the car’s front spoiler. By the way, fog lights have a similar tendency to become covered by a thick sheet of snow, and so rendered practically useless in wintry conditions.
Headlights are less impacted by this problem, partly because they are mounted higher up. What’s more, because of the heat they generate during operation, halogen-powered headlamps are able to free themselves of ice and snow to some degree. Xenon headlamps and LEDs are not so good in this respect – producing less waste heat due to their higher efficiency. Thankfully, most widely-used xenon headlights are fitted with cleaning systems that ensure they can shine brightly in all weathers. Drivers only need to make sure they switch them on – and not just their daytime running lights!