[Driving with light during the day?].

In various Scandinavian countries the use of headlights during daytime (daytime running light DRL) is obligatory since many years. In Canada all new cars have to be equipped with a daytime running light since 1990. Whether or not in Germany or in the southern neighbouring countries a daytime running light should be used is matter of controversial discussion during the least years. Daytime running light increases the visibility of oncoming cars tremendously. Not only the drivers, but also pedestrians and cyclists profit from this gain of visibility. Especially drivers with poor vision, who will become more and more frequent during the coming years due to the increase of percentage of older drivers, have a specific profit from daytime running light. Potentially negative side-effects of daytime running light are: reduction of visibility of the brake-lights, glare, loss of visibility for pedestrians and cyclists, damage to the retina, increase of fuel consumption. All these arguments are either not crucial or cannot be documented by statistical data. On the other hand the data which are available up to now concerning frequency of accidents in those countries and areas in which daytime running light was used or is used, show a trend, sometimes even a statistical significant reduction of daytime accidents. This reduction is especially pronounced for accidents with pedestrians and cyclists. Overall, there are more and better arguments for using daytime running light, also in Germany. A technical alternative would be an automatic switching of the headlights if horizontal illuminance drops below a specific limit, e.g. 2000-3000 lx. Such an automatic procedure would increase the percentage of cars using headlights in critical situations during daytime.