The Effect of Vertical Acceleration on Emergency Locking Seatbelt Retractors

Contemporary production seatbelt retractors have been proven very effective in the crash environment for which they have been primarily designed and most adequately tested, that is, in the full frontal crash mode. The National Traffic and Motor Vehicle Safety Act of 1966 outlines specific crash test and occupant injury measure requirements for testing and evaluation of seatbelt systems in production vehicles. Automobile manufacturers routinely test exhaustively in compliance of these requirements with respect to full frontal barrier crashes. However, government requirements are not nearly as complete for alternative accident modes often seen in the real world. Offset, angled, override, underride, and rollover crashes will often require seatbelt retractors to manage acceleration pulses in varying directions, including the vertical plane. Occupant motions during these real world accident modes may also impart loads into the belts and belt hardware (webbing and buckle assemblies) that also may not be immediately apparent in the frontal barrier test mode.