1Swedish Road and Traffic Research Institute
Collisions between road users are the most serious and frequent road traffic accidents. When trying to look deeper into the question why a collision really happened a frequent and true answer is that the other road user was not detected until too late. Certainly accidents may happen in spite of detection, e.g, due to misjudgement of speed and/or distance. But early detection is a necessary condition for safe road traffic.
For most road users the most dangerous vehicle in road traffic is the automobile (the truck, the bus, the passenger car). Therefore, the most important conspicuity is that of the automobile. It is true that the highest risk is that for the motorcycle. But even if the risk is high the accident frequency and the risk for others are low.
Vehicle conspicuity can be obtained at least four ways;
For several reasons internal motion and angular size are not workable variables. Information technology is probably the solution of the future-but not today. Contrast can be obtained by choice of colour. But the effects in some situations are not too good. Another way is the use of lights on the vehicle. Specially in levels of lower ambient illumination lights on vehicles (DRL: Daytime Running Lights) call attention in the periphery of the visual field—detection!
In Sweden, Finland, and Norway DRL has been successfully tried as a conspicuity enhancing and accident reducing measure. In Canada, the Netherlands, and Austria the question of compulsory DRL is close to a solution. An account will be made of the advantages and problems with DRL.