Road safety is often expressed as the annual number of fatalities or the number of killed and seriously injured (KSI) in road accidents. The number of victims is strongly related to the distance travelled, as a measure of mobility. Therefore, the focus in road safety research is often not on the number of victims, but on the risk which is defined as the number of victims per distance travelled. Road safety assessment modelling aims at understanding the development of road safety by describing the relation between road safety and the factors that influence road safety. In this paper, the results of the feasibility study of our project to develop a road safety assessment model for the Netherlands are presented. The key aspect of the method used is multiple disaggregation, or in other words looking at (the development within) subgroups. These disaggregations may allow us to see differences which cannot be seen at the aggregated level. So far, we restricted ourselves to a subset of the traffic process (cars and bicycles only) and to disaggregation by only one extra factor (age). The results presented here are essentially an empirical smoothing of the disaggregated data. In a later stage we will switch to mathematical modelling which includes parameterization and statistics by introducing a structural time series model using state space methods. (Author/publisher)
Samenvatting