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Headlight Use for Vehicles during Daylight Hours - Experience and Results in Road Safety
The idea with lights on during daylight, or Daytime Running Lights (DRL) as they are nowadays called, was to enhance vehicle conspicuity. The background was that late detection is one of the most frequent driver explanations for collisions. DRL were studied in the USA in the 60ies and introduced on some fleets (e.g. Greyhound). The experiences were good. But the studies were not very well carried out.
In Sweden the idea was taken up in the 60ies. Detection experiments were carried out in peripheral and central vision and special DRL-lamps for cars were developed and sold. In connection with the transition from left to right hand traffic in Sweden 1967 DRL (low beams) were recommended on all motor vehicles. Based on analysis of crash statistics the Nordic Road Safety Committee decided in the 70ies to recommend compulsory DRL on all cars. The estimated effect of DRL was a reduction of daytime collisions of about 15 %. In the Nordic countries the experiences are good and there are no thoughts of repealing the DRL legislation.
In 1977 DRL were made compulsory in Finland and Sweden. Norway followed 1985 and Denmark 1990. In Canada it was decided that all new cars should have DRL from 1989. Many studies of DRL effects on crash statistics have been carried out in several countries. They all show reduction of daytime collisions as an effect of DRL in the size of 10 to 15 %. Unprotected road users seem to benefit more from DRL than drivers of cars. The explanation is probably their larger dependence of peripheral detection. The positive effect of DRL is probably larger closer to the poles. The main counter-arguments are increased fuel consumption and pollution. Also the motorcyclists argue that their advantage of DRL will be reduced if all motor vehicles have DRL.
Many technical solutions have been tried. The most common and simple one is still normal or reduced low beams. The switching of the DRL is now automatic. In the USA some car makes have DRL (e.g. GM). Today many other countries have more or less general DRL legislation (e.g. Hungary, Poland). Special DRL analyses have been carried out in the EU and compulsory DRL is presently proposed and discussed as an effective road safety measure. The calculated percentage of crash reduction varies from about 10% for multiple daytime crashes to about 25% for fatalities in multiple daytime crashes. The calculated benefit/cost ratio is 1.80. The estimated reduction of traffic fatalities within EU is 5.500 per year!