Influence of pre-crash driver posture on injury outcome: airbag interaction with human upper extremities

Abstract

This study will investigate the effect of pre-collision occupant posture on the injury outcome during collisions. The main objective of this study is to quantify the dynamic response of human upper extremities under airbag deployment in the adverse forearm position identified from the previous volunteer survey on driving simulator (e.g. the forearm placed in front of the steering wheel). The variability in the postural orientation of the driver, during emergency vehicle maneuvers, was recorded in a volunteer survey on a car driving simulator, through videos of occupants, in a virtual frontal collision scenario with a truck. The main result was that none of the subjects adopted the standard driving position used in crash experiments. The typical response to this type of emergency event was to brace rearward into the seat and to straighten the arms against the steering wheel, or, to swerve to attempt to avoid the impacting vehicle. The influence of this out-of-position (OOP) on injury outcome was extensively investigated with Hybrid III dummy but was restricted by a limited insight on upper extremity skeletal injury patterns. A critical OOP was identified through real-life driver posture observations at time of crash in a previous volunteer survey on a car driving simulator. This OOP position corresponded to a driver forearm in front of the steering wheel as in avoidance maneuvers. Static-airbag deployments were realized experimentally with post mortem human subjects (PMHS) upper extremities fixed to a Hybrid III dummy. Airbag membrane loading were realized with the virtual validated Madymow human model. In the experimental approach, bone fractures were observed in the third distal forearm bones. Similarly, excessive strains were observed in these areas in the numerical model. In both cases, injuries were due to direct impact with the airbag membrane. The experimental protocol will be extended later to fresh male human anatomic segments. Bone failure model will be developed for a better prediction of skeleton injuries.