Rotational acceleration as a traumatic brain injury mechanism in pedestrian - vehicle collisions

Around 15% of all the traffic related fatalities in Europe are pedestrians. That is 6500 fatalities in Europe. Head injury is the most severe injury in the pedestrian pattern and together with the lower extremities the only anatomical areas where countermeasures are applied. Head injury in the automotive industry is predicted through the Head Injury Criterion (HIC). All the countermeasures applied and all the regulations derived from them are focused on this criteria. The HIC only uses as an input the linear acceleration measured in the head Centre of Gravity. In this dissertation rotational acceleration as a risk factor for traumatic brain injury in pedestrian-vehicle collisions has been evaluated, and compared with the main injury criteria accepted by the scientific community. An Epidemiologic transversal and descriptive study has been performed using the pedestrian crash data study (PCDS) database. This database shows the importance of head injuries in pedestrian-vehicle collisions and the different injury sources. In the case of adults the windshield is the main structure involved in head injuries, whereas in the case of children the main structure is the hood. Crossing the PCDS with a Transformation matrix developed by Dr. Martin, was evaluated the proportion of injuries produced by rotational acceleration, pure rotational acceleration as a injury mechanism was shown to be almost twice as important as pure linear acceleration. Sled tests with two different vehicles (a Sedan and a SUV) involving 5 Post Mortem Human Surrogates (PMHS) were instrumented and tested to measure head linear and rotational velocity in case of pedestrian collision. These data were processed and translated to the PMHS head CG. Also impact locations were recorded and compared with the current European Directive 2003/102/CE and EuroNCAP Protocol version 4.1.