Influence of the chest compression measurement method on assessment of restraint performance in side-impact crash scenarios

Side impact crashes contribute a significant number of fatal injuries (25% of road fatalities in the USA in 2016), with severe thoracic injuries diagnosed in 58% of front near-side impact occupants. Epidemiological data indicate that thoracic-only side airbags (tSABs) are not as effective as laboratory testing has suggested, and one of the reasons for this may be the use of surrogate-specific injury assessment methods, which are not directly transferable between Anthropometric Test Devices (ATDs) and Post-Mortem Human Surrogates (PMHSs). This study examines the effect of the thorax deformation measurement location and method on the predicted performance of seatbelts and tSABs in a side impact using a Human Body Model (HBM). The HBM was integrated in a vehicle and subjected to a Moving Deformable Barrier (MDB) impact at 61 km/h, with four restraint configurations: belted and unbelted, with and without a tSAB. Occupant response was assessed through chest band (CB) deformation, and as a change in distance between markers on the ribs. Multiple measurement locations in the HBM enabled direct comparison between the methods. The CB method indicated a 35% increase of chest compression due to tSAB; the rib-deflection (RD) method was not sensitive to the tSAB. The RD method predicted a 20% reduction of chest compression due to the seatbelt, but the CB-measured change was negligible. This study highlights the importance of measurement method on the response outcome and demonstrates that different outcomes may be predicted using a HBM for the same impact scenario, depending on the measurement method.