Stiffness of passenger cars: a class analysis

The increase in traffic flows on the roads causes an increase in road accidents. The study of the road safety deals on how to reduce the related phenomenon to non-pathological levels; to be able to operate correctly, much different information are needed. For some different levels of investigation of the phenomenon, only the incidental statistics may be necessary. To plan the interventions it needs information on the single incidents that occur in some areas. Each incident has some evolution characteristics that are repeated in a non-random manner, and these recurrences must be highlighted and studied to obtain effective countermeasures. The study methodologies of the road accidents maybe not only on their typology and imply the possibility of reconstruction, even if approximate, of the incident and its temporal phases of development. In some cases, it may also be necessary to evaluate the impact speed between vehicles. Some incident reconstruction techniques allow obtaining reliable speed values before the impact starting from the evidence left on the roadway. If these are not present, it is possible to use methodologies that provide speed values starting from the deformations of the vehicles as a relationship to the structural stiffness coefficients. Some databases are available: these concerning the coefficients obtained for a number of passenger cars and Others concerning sister cars: these are used with a reasonable degree of approximation in forensic engineering works. A road safety engineer may not need values with a high degree of approximation but may wish to proceed more quickly with some stiffness coefficients that are not exactly those of a single model of car but only for those of car that has similar characteristics, not equal, with the full advantage of the speed of accident reconstruction. In research work, different stiffness coefficients for passenger cars were analysed and grouped for displacement classes, length and pitch.