Understanding the Influence of Seat Belt Geometries on Belt-to-Pelvis Angle Can Help Prevent Submarining

The first objective of this study, addressed in Part 1, is to use finite element (FE) human body modeling (HBM) to evaluate the tangent of the Belt-to-Pelvis angle (tanθ_BTP) as a submarining predictor in frontal crashes for occupants in reclined seats. The second objective, addressed in Part 2, is to use this predictor to assess two technical solutions for reducing submarining risks for two different occupant anthropometries.

In Part 1, tanθ_BTP (the lap belt penetration from the anterior superior iliac spine [ASIS] in the abdominal direction) was evaluated in impact simulations with varying seat belt anchor positions. Sled simulations with a 56 km/h full-frontal crash pulse were performed with the SAFER HBM morphed to the anthropometry of a small female and average male. A correlation was found between the submarining predictor and submarining.

In Part 2, the anti-submarining solutions (i) split buckle belt system and (ii) anchor moving system were evaluated using the submarining predictor from Part 1. The split buckle belt system was found to reduce the tanθ_BTP on the buckle side, due to the disconnection from the diagonal shoulder belt force. The anchor moving system, in contrast, was found to reduce the tanθ_BTP for both buckle and lap sides. Thus both systems reduced submarining risk.

Part 1 showed that the tanθ_BTP is an accurate geometry-based submarining predictor. Part 2 demonstrated that both the split buckle belt system and the anchor moving system reduce submarining risks, as predicted by the tanθ_BTP.