Impact severity assessment in vehicle accidents

The severity of the impact in a car accident is an essential parameter for evaluating the performance of the vehicles in terms of passive safety, as well as to compare different accidents and be able to correlate structural and kinematic parameters to the occupant's injuries. In assessment programmes, like the European New Car Assessment Programme (EuroNCAP), impact severity plays an essential role in the evaluation of the adequacy and representativeness of the experimental tests in relation to real-life accident conditions. In the present paper, two dimensionless indexes are considered, the crash severity and the crash momentum index. Starting from the available formulation, only valid for plastic centred impacts, these indexes are generalised to the case of oblique impacts and not necessarily plastic, by expressing them as a function of the ratio between the vehicles masses and stiffness, and as a function of the vehicles configuration at impact. With this generalisation, indexes can be used in the analysis and comparison of real world accidents. Typical applications of the indexes are discussed and a comparison between an EuroNCAP test and a crash that simulates the impact between two vehicles in a typical configuration of an urban accident is carried out