Factors That Influence Chest Injuries in Rollovers

Objectives: The design of countermeasures to reduce serious chest injuries for belted occupants involved in rollover crashes requires an understanding of the cause of these injuries and of the test conditions to assure the effectiveness of the countermeasures. This study defines rollover environments and occupant-to-vehicle interactions that cause chest injuries for belted drivers. Methods: The NASS-CDS was examined to determine the frequency and crash severity for belted drivers with serious (Abbreviated Injury Scale [AIS] 3+) chest injuries in rollovers. Case studies of NASS crashes with serious chest injuries sustained by belted front occupants were undertaken and damage patterns were determined. Vehicle rollover tests with dummies were examined to determine occupant motion in crashes with damage similar to that observed in the NASS cases. Computer simulations were performed to further explore factors that could contribute to chest injury. Finite element model (FEM) vehicle models with both the FEM Hybrid III dummy and THUMS human model were used in the simulations. Results: Simulation of rollovers with 6 quarter-turns or less indicated that increases in the vehicle pitch, either positive or negative, increased the severity of dummy chest loadings. This finding was consistent with vehicle damage observations from NASS cases. For the far-side occupant, the maximum chest loadings were caused by belt and side interactions during the third quarter-turn and by the center console loading during the fourth quarter-turn. The results showed that the THUMS dummy produced more realistic kinematics and improved insights into skeletal and chest organ loadings compared to the Hybrid III dummy. Conclusions: These results suggest that a dynamic rollover test to encourage chest injury reduction countermeasures should induce a roll of at least 4 quarter-turns and should also include initial vehicle pitch and/or yaw so that the vehicle's axis of rotation is not aligned with its inertial roll axis during the initial stage of the rollover.