Four steer-induced rollover crashes were analyzed by calculating the local three-dimensional accelerations at hypothetical seat positions’ Emergency Locking [seat belt] Retractor (ELR). The method for calculating the local acceleration was described in a recent Society of Automotive Engineers (SAE) paper and assumed three-dimensional rigid body motion, recorded acceleration and recorded roll rates at the center of gravity. For a threshold of 0.7 g, results demonstrated that intervals in the vehicle’s response that may cause the ELR’s inertial sensor to move into a neutral zone were limited to localized high-magnitude negative vertical acceleration events during the rollover segment with a maximum calculated duration of 31.7 ms. Changing the threshold to 0.35 g reduced the interval count by 70 percent and maximum duration by approximately 50 percent. Results of the analysis were consistent with prior published research that noted limited and brief periods of instances in rollover crashes when the inertial sensor may be in a neutral zone. Calculating an interval that a vehicle’s response may allow a retractor to move into a neutral zone did not mean that a specific retractor will move into a neutral zone. To asses if a specific retractor will move into a neutral zone its performance should be analyzed. As identified in prior research, occupant kinematics analysis was necessary in determining whether an inertial sensor in a neutral zone during a rollover event will result in belt spool out. It is beyond the scope of the paper to include a complete analysis of occupants’ kinematics.

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