The impact of changes in the proportion of unexperienced car driving on the annual number of road deaths


Stipdonk, H.




The annual number of road deaths in the Netherlands and other high income countries is featured by a summit around 1970. However, for different types of fatal road crashes (pedestrians killed by a car, car single vehicle crashes, car-car crashes etcetera), trends and trend changes are quite different. The paper shows the principles of a possible mechanism to incorporate an experience factor in the analysis of road death data. Changes in (trends in) the annual number of groups of fatal crashes are shown to coincide with changes in the proportion of inexperienced car drivers.

Three selected groups of crashes for which annual car distance travelled has been a main relevant factor were analysed: car single vehicle crashes (CS), pedestrian-car crashes (PC) and car-car crashes (CC). We used data of total car distance travelled since 1950, and car fleet data since 1946 to estimate the car distance travelled stratified by driver’s experience. We assumed that annual car fleet increase corresponded to the introduction of new cohorts of car drivers.

To model the experience factor in risk (fatal crashes divided by car distance travelled) for CS and PC crashes we assumed this factor to be a simple parametrized function, decreasing with driver’s experience and dependent on the age drivers start their driving career. For CC crashes we incorporated the effect of experience factor and distance travelled for two car drivers simultaneously. For each crash group we assume a parametrized negative exponential risk decrease to model the influence of all other risk factors.

The results show considerable resemblance between model values and road death data for each of the three groups. The method enables comparison between the risk trends for the three fatality groups. The presented method can be further improved, e.g. by adding the effect of increase risk for ageing drivers.

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Proceedings of the 6th International Conference on Road Safety & Simulation (RSS), 17-19 October 2017, The Hague