Evaluation of Road Equipment with Emphasis on Condition Assessment

Sammanfattning: This doctoral thesis deals primarily with condition assessment of road equipment. The road equipment concept is defined by five main groups, road lighting, fences and barriers, vertical signs, horizontal signs and traffic signals, respectively. Of these groups, road markings, street lighting and barriers of three-lane roads have been studied more in detail.A state-of-the-art, comprising information obtained by comprehensive literature studies on condition assessment of road equipment is presented. Comparably few fundamental studies were found, which, to some degree, can be explained by the lack of suitable physical measurement methods. However, in the case of road marking retroreflectivity, mobile instruments have been developed, and research published in this area is relatively comprehensive. Furthermore, although not based on mobile measurements, several studies on assessments on performance of road sign sheeting have been published.The experimental part of the thesis is divided into four studies, of which two are dealing with mobile measurement of wet road markings and street lighting, respectively. One of the studies concerns condition assessment of road marking performance accomplished in the Nordic countries. Finally, one study comprises risk analysis related to crashes into the barriers on three-lane roads. At road equipment condition assessment, mobile measurement methods are preferable compared to stationary methods. However, many relevant parameters are tricky to measure at speed. One example in this connection is characterization of performance of wet road markings, which has to be based on one or more parameters obtained by measurements on dry surfaces. Results presented in this thesis indicate that retroreflectivity and skid resistance of wet road markings can be predicted based on retroreflectivity and macro-texture of dry road marking.For traffic safety, street lighting is important. The performance of this type of road equipment is in most cases described in terms of luminance of the illuminated road surface. However, luminance measurements are tricky and time-consuming and not useful for condition assessment. On the contrary, measurement of illuminance is easy to carry out and can be performed at speed. One part of the thesis describes how road surface luminance in street lighting can be estimated based on illuminance and reflection properties of the road surface. With the purpose of comparing road marking performance in the Nordic countries, condition assessment using mobile measurement equipment was accomplished in 2002 and 2003. In each of the five Nordic countries, a number of roads were chosen for measuring retroreflectivity. The study showed that the retroreflectivity of edge, centre and lane lines was poor in some countries, but, at least regarding edge lines, this shortcoming could be compensated by use of wide, continuous lines. In other words, the visibility of longitudinal road markings was approximately equal in the different countries.The purpose of the risk analysis performed on three-lane road barriers was to estimate the influence of the time-period between initial crash and repair on the risk of a secondary accident. The result showed that, especially in winter-time, time-reduction means reduced risk of secondary accidents.