Influence of road surfaces on target visibility: experimental measurements
Résumé
Street lighting ensures visibility and legibility for road users. In this paper, performances of the lighting installation of two road sections with different type of road surface are measured in accordance with guidelines and road lighting standards. Then, the calculation of the visibility level of a target according to the Adrian’s model is included considering the light reflections on the road. We compare the results obtained for each section with and without considering the light reflections and conclude that there is an incidence of the nature of the road surface on the target luminance. However, the effect on the visibility level of the target is not so straightforward. This depends on whether it is close to the visibility threshold, and it is therefore important to consider the reflective properties of the road surface. Moreover, we see that the visibility level provides us more information than the classical descriptors. The same luminance distribution for two pavement/lighting couples does not necessarily lead to the same distribution in terms of target visibility. It seems necessary to us to reinstate the visibility level in the performance criteria defined by the standard because it would act as a local descriptor of the performance of the pavement/lighting combination and would thus make it possible to avoid safety problems.