The Effect of Pre-Crash Velocity Reduction on Occupant Response Using a Human Body Finite Element Model

<b>Objective</b>: The objective of this study is to use a validated finite element model of the human body and a certified model of an ATD to evaluate the effect of simulated pre-crash braking on driver kinematics, restraint loads, body loads and computed injury criteria in four commonly-injured body regions. <b>Methods</b>: The Global Human Body Models Consortium (GHBMC) 50th percentile male occupant (M50-O) and the Humanetics Hybrid-III 50^th percentile models were gravity settled in the driver position of a generic interior equipped with an advanced three point belt and driver airbag. Fifteen simulations per model (30 total) were conducted, including four scenarios at three severity levels: median, severe, and US-NCAP and three extra per model with high intensity braking. The four scenarios were: No pre-collision system (No PCS), forward collision warning (FCW), FCW with pre-braking assist (FCW+PBA), and FCW and PBA with autonomous pre-crash braking (FCW+PBA+PB). The baseline ΔV was 17 kph, 34 kph and 56.4 kph for median, severe and US-NCAP scenarios, respectively, and were based on crash reconstructions from NASS/CDS. Pulses were then developed based on the assumed pre-crash systems equipped. Restraint properties and the generic pulse used were based on literature. <b>Results</b>: In median crash severity cases, little to no risk (&lt;10% risk for AIS 3+) was found for all injury measures for both models. In the severe set of cases, little to no risk for AIS 3+ injury was also found for all injury measures. In NCAP cases, highest risk was typically found with No PCS and lowest with FCW+PBA+PB. In the higher intensity braking cases (1.0 – 1.4 g) HIC, BrIC and chest deflection injury measures increased with increased braking intensity. All other measures for these cases tended to decrease. The ATD also predicted and trended similarly to the human body models predictions for both the median, severe and NCAP cases. Forward excursion for both models decreased across median, severe and NCAP cases and diverged from each other in cases above 1.0 g's of braking intensity. <b>Conclusions</b>: The addition of pre-crash systems simulated through reduced pre-crash speeds caused reductions in some injury criteria, while others (chest deflection, HIC, and BrIC) increased due to a modified occupant position. The human model and ATD models trended similar in nearly all cases with greater risk indicated in the human model. These results suggest the need for integrated safety systems that have restraints that optimize the occupant's position during pre-crash braking and prior to impact.