Abstract
The common method to determine the effect of road lighting on traffic safety, is to compare accident numbers during daylight and darkness, before and after the measure is taken. This approach ignores the possibility of increased risk of collisions with road side obstacles due to the erection of lighting poles. Both effects should be taken into account if decision making on road lighting has to be based on a cost-effectiveness-criterion for traffic safety. A scheme for decision making, based on a more complete determination of consequences of road lighting systems is presented.