The relationship between spontaneous choice of speed and lighting level on streets with stationary light has been studied. On ten streets in Linköping, the speed of cars which were not disturbed by other traffic, was measured. One important question was if low lighting levels would result in lower speeds that would compensate for the worse visibility of objects in or close to the street. If so, there would be a positive effect on energy and environment without making impairing traffic safety. The results shows a tendency that reducing the lighting level with 50 % will admittedly reduce speed, but with approximately 3 %, only. Furthermore, the reduction of lighting level will decrease the visibility distance of a pedestrian at a zebra crossing from on average 118 m to 95 m, or 23 %. However, still the visibility distance is much longer than the stopping distance at 50 km/h, and the decrease in visibility, in most driving situations, might not be critical. The visibility distance indicates the longest distance at which an object can be detected, e.g. at a zebra crossing, where the driver has an expectation that there might be a pedestrian waiting to cross the street. One question raised is at which distance the pedestrian would be detected if the driver has no such expectation, e.g. between two zebra crossings. Most certain, this distance is shorter than the visibility distance, but could it be that short that the risk of hitting an object increases? (Author/publisher)
Abstract