Australia is facing an ageing and polarising-market passenger vehicle fleet. Changes in the composition may have substantial road safety implications in terms of the fleet?s overall crashworthiness. This study focuses on Victoria, and assesses the current and past passenger fleet composition in terms of vehicle age by market group. Based on current trends, such as population rates, new vehicle sales and market group trends, a scrappage function by age of vehicle is estimated to project the vehicle fleet to 2012. By manipulating key inputs and outputs to the system, deviations from this baseline projection are estimated from a range of scenarios, to examine changes in vehicle fleet composition from various external influences to the system. The overall purpose of this estimation procedure will be in estimating the crashworthiness, and intrinsically aggressivity, of those projected fleets to give an overall estimation of fleet crashworthiness under the various scenarios. This will help to determine the effect of a particular change to the system, for example a policy change, and to measure the effect on the overall safety of the vehicle fleet over time.