Assessment of Vehicle and Restraint Design Changes for Mitigating Rear Seat Occupant Injuries

<div><p><b>Objective:</b> Investigate the combined effects of belt geometry, seat substructure, and seat belt pretensioners and load limiters on rear seat occupant injury risk.</p><p><b>Methods:</b> An instrumented Hybrid III 5th percentile adult female dummy was subjected to simulated frontal impacts (Δ<i>v</i> = 45.8 km/h, peak acceleration = 27.1 <i>g</i>). Testing was conducted on a rear seat of a typical family sedan with modifications allowing for adjustment in upper anchorage position, mounting of an antisubmarining seat pan, and the use of seat belt pretensioners with load limiters.</p><p><b>Results:</b> Dummy seated posture had the strongest effect on submarining. Seat belt pretensioners with load limiters reduced head and femur excursion and decreased chest injury measurements but did not prevent submarining. The antisubmarining seat pan, on the other hand, prevented submarining in one case but could not prevent submarining with the dummy in a slouched posture. Upper anchorage position resulting in poor belt geometry was shown to increase both chest injury measures and submarining.</p><p><b>Conclusions:</b> The results from this study demonstrate the importance of an upright seated posture and the potential benefits of including adjustable upper anchorages to allow good sash belt fit, antisubmarining seat pans, belt buckles positioned near the seat bight, and seat belts with pretensioners and load limiters for rear seat occupants. These data can be used to inform the design of a system of restraints to reduce injuries to rear seat occupants.</p></div>