A Model for Considering the ‘total Safety’ of the Light Passenger Vehicle Fleet

This report describes the results of research to develop and apply a comprehensive model to consider the influence of the mix of vehicle types on the total safety of the light passenger vehicle fleet in Australia. Key inputs to the model are estimates of the crashworthiness and aggressivity of light passenger vehicles in the key crash types representing the majority of crashes in which these vehicles are involved. They include crashes between two light vehicles, single vehicle crashes, crashes with heavy vehicles and crashes with unprotected road users such as pedestrians and bicyclists. The model combines these key crashworthiness inputs with measures of crash exposure of each vehicle class in the fleet mix to estimate the average injury outcome in all crashes involving the light vehicle fleet. By varying the key parameters of the model, it was possible to examine the effects on the average safety of the light vehicle fleet resulting from changes to the mix of types of vehicles in the fleet. Application of the model was demonstrated through a number of scenarios varying the mix of vehicles in the fleet by broad market group classification. Scenarios considered include natural changes in market group mix of the fleet in recent times and projected over the next 10 years, elimination of various market groups from the fleet, homogeneous fleets composed of a single market group, and fleets composed of only vehicles with the best possible safety performance in each market group. Results of applying the model to the various scenarios considered point to how the vehicle fleet mix might best be manipulated in the future to optimise safety outcomes. Safety outcomes resulting from recent current and projected future trends in vehicle fleet mix were also able to be quantified.