In the SWOV study entitled Route choice in a road network, we wish to investigate the possibilities for influencing the route choice of motor vehicle drivers in such a way that the route meets one of Sustainable Safety's functional requirements, viz. the quickest and safest routes are one and the same. It has previously been shown that microsimulation models are a suitable aid for route choice studies. They make it possible to examine beforehand how the route choice will change as a result of new or adapted facilities alongside or on the roads, or in vehicles. Studies of the safety of route choice, or changes in route choice, require safety indicators. In this report these indicators are formulated and applied in a test network in a microsimulation model. We chose two types of road safety indicators: general and vehicle-dependent. The general indicators are independent of the traffic volume on a road network. They are derived from the route characteristics that are closely related to road safety, such as the route length or the number and type of transitions between different road types. These general safety criteria are rooted in the 'route diagram' which is a method of visualizing the Sustainable Safety character of a route. The correct route diagram shows a journey that contains all road types in the correct sequence and in the correct proportions of length. The deviation from the correct diagram determines how unsafe the presumed route is. Thus the route diagram expresses a qualitative safety that can be translated into quantitative criteria. The vehicle-dependent indicators allow for the real-time traffic situation on the network. They express the extent to which vehicles encounter other vehicles along a route and how these meetings end; these are 'conflict indicators'. The mass of the vehicles, their direction, speed, and lateral position largely determine the severity of conflicts. We are still speaking here of calculated conflicts in a simulation model; in other words not of real conflicts, let alone near-misses. The results of the calculation methods used do not all give the same safety effects of route choice. Further research is necessary to find the explanation for this and to determine the methods' utility. In principle, the route choice safety criteria are suitable for (computer) programs used in route planners. Applying the microsimulation model to a test network is insufficient for deciding on whether such models are a suitable road safety research instrument. To do this, a microsimulation must be tried out on a real-life road network, and the registered safety, usually expressed in crashes, should be compared with the calculated safety.
Samenvatting