Minimal Effect of Amplified Vehicle Accelerations on Seat Belt Buckle Resistance to Inertial Release

Detailed investigations continually demonstrate that vehicle collision environments are extremely unlikely to produce accelerations of sufficient magnitude and duration to cause inertial release of seat belt buckles. Recently, it has been proposed that the dynamic response of an end-release buckle mounted to the vehicle structure via a metal strap or wire rope can amplify acceleration levels experienced at the floor of the vehicle by a factor of 10 or more, to levels that are high enough to cause inertial release. Experiments and modeling presented here confirm that accelerations may be amplified from the floor of the vehicle to the seat belt buckle, but not by more than a factor of 1.3, and only for acceleration pulse durations that are very short. Shock table testing of end-release seat belt buckles shows that, even with amplification, the resulting buckle accelerations are far below those required to cause inertial release, even at very low webbing tension.