En route to safer roads. How road structure and road classification can affect road safety

Atze Dijkstra investigated whether road safety can be improved by making changes in road structure and road categorization according to the functional requirements of Sustainable Safety. One of these demands is that the fastest route is also the safest route. This is often not the case in practice. The results of this research will make it possible to check in the planning and design phases of a road network to which extent it will meet the Sustainable Safety requirements. Several (new) types of research methods and safety indicators were used to answer these questions. The road network has been analysed using the so-called (adapted) Integrated Network Design method. The safety aspects of routes have been determined using three safety indicators: a route score which describes the safety of a route (DV score), the number of conflicts that has been calculated in a microsimulation model (calculated conflicts), and the number of registered crashes. The number of calculated conflicts has a quantitative relation with the number of crashes, and the number of conflicts has a quantitative relation with the route score. Indirectly, through the number of conflicts, there is a relation between the DV score and the number of crashes. The DV score is therefore relevant for road safety research. In a study area, several routes with the same origin-destination relation have been investigated. The comparison of their DV scores shows that, among other things, the fastest route and the most chosen route do not always have the best scores. The safety of the routes that were travelled has afterwards also been calculated using crash rates. This indicates that the fastest routes are significantly less safe than the safest routes. These results are dependent on the given network in the study area. Adaptation of the network can change the results. The present study shows that presently the safest route often fails to be also the fastest route. Because drivers usually choose the fastest route, the author recommends developing policy to ensure that the fastest route is also the safest route.