Position and rotation of driver's head as risk factor for whiplash in rear impacts

Evidence suggests that head position increases risk of whiplash injury to vehicle occupants in rear impacts. The aims of this study were to collect exposure data on head position and rotation during naturalistic driving and to express this in the form of a parametric statistical model for use in computer simulations to optimize seat design for neck injury prevention. An instrumented vehicle equipped with an eye-tracker was used to collect digital readings that were complemented with a four-track video recording. Data from driving trials (approximately 30-60 minutes) were analyzed when the vehicle was stopped, stopping or moving slowly as these are thought to be manoeuvres where impact and hence neck injury risk is highest. It was found that the ‘t location-scale’ distribution provided best fit to the experimental data and that the measured interquartile range or central 50% of head movement in such manoeuvres was approximately ± 15 mm lateral, ± 10 mm longitudinal and ± 7.5 degrees left-right rotation. These ranges provide guidance on the degree of biofidelity required in computer simulation models. Further analysis showed that out-of-range head rotation and rapid rotation explained the majority of missing digital readings and these two motions should therefore be modeled separately as elements of the parametric model.