Injury risk in real world crashes is often estimated using the vehicle change in velocity (delta-v) in a crash. Delta-v however, does not consider either the crash pulse or occupant restraint system. This study considers two alternatives, the Occupant Load Criterion (OLC) and the Acceleration Severity Index (ASI) in 140 frontal, vehicle to barrier, 56 km/h New Car Assessment Program (NCAP) crash tests. Both OLC and ASI account for varying crash pulses with a basic model of restraints. Event Data Recorders (EDRs) can provide a direct measure of delta-v and the crash pulse. The first research question was whether the OLC and ASI are good predictors of injury metrics. Second, in order to apply the injury correlations to real world crashes, the second aim was to determine whether EDR data could accurately capture the OLC and ASI metrics. These vehicle-based metrics were first compared to four common injury metrics, the Head Injury Criterion (HIC), 3 ms clip chest acceleration, peak chest displacement, and peak pelvic acceleration using the crash test instrumentation data but showed little correlation with these injury criteria.

Next, with the ultimate goal of the study being to evaluate the vehicle-based metrics for EDRs to assess real world crashes, maximum delta-v, OLC, and ASI values were calculated from the EDR longitudinal velocity data and compared with the same metrics computed from crash test accelerometers. Mean percent differences were minimal, below 6%, for both the maximum delta-v and ASI metrics, with the EDRs underreporting values. The OLC mean percent difference for the 140 cases was -16.4%, showing poor agreement with the crash test instrumentation metrics. However, a number of the cases did not appear to record a complete EDR crash pulse. When only evaluating the 110 of the 140 cases with crash pulse complete status, the mean percent difference for the OLC was reduced to -6.82% and the ASI and maximum delta-v differences remained relatively unchanged. This exploratory study has shown that the OLC and ASI vehicle-based metrics do not appear to correlate well with accepted injury metrics gathered from instrumented ATDs in controlled NCAP crash tests with impact speeds of 56 km/h. Additionally, for implementation in real-world scenarios using EDRs, the accuracy of the EDRs and the completeness of the crash pulse recorded by the EDRs should be considered when evaluating some vehicle-based crash metrics. Specifically, OLC values are negatively affected by incomplete crash pulses while ASI values are more independent of the completion of the crash pulse.