A forecasting road safety model presented. SWOV has developed a forecasting road safety model. In 2011, this model will be used in making the Road Safety Outlook 2020, but it can also be used for other purposes. The present report discusses how the model can be used to make an estimate of the number of road fatalities and serious road injuries in a future target year. The forecasting model has been composed from several submodels, the results of which yield the total expected number of casualties when added together. Several models are required because the development of the number of casualties varies greatly for different types of conflict. Some types of conflict, like those not involving a motorized vehicle, have been showing an upward trend in casualty numbers for years, whereas other groups of casualties, like car occupants, are going down in number. The report describes which subgroups are distinguished and how the future safety developments for each subgroup are estimated. For all groups of casualties, a distinction is made by age of the drivers involved, who are not necessarily the casualties. This is done because the crash involvement is strongly related with the drivers' age, and because the composition of the population is characterized by relevant shifts. The model takes account of these shifts by relating data to the size of the population by age. The model uses mobility as the most important factor of influence. When mobility increases, a decrease in safety must be expected, unless there has been such a road safety improvement that the casualty rate (the number of casualties per distance travelled) has decreased sufficiently. Different kinds of mobility are important for different groups of casualties. Casualties in crashes with passenger cars are related to car mobility; bicycle mobility plays a role in bicycle crashes. For a proportion of the crashes, e.g. crashes in which neither cars nor bicycles are involved, the mobility data (by age) often is too inaccurate to be used in modelling. In that case the model reverts to population data. The present report describes the approach that was followed and gives examples of the way in which a prognosis can be made for 2020. Exemplary values have been used for the expected mobility. Therefore, the results presented in the report cannot be considered to be the expected number of casualties in 2020; this requires using correct estimates for bicycle and car mobility by age as well as population data.
Abstract