US and UK Belted Driver Injuries with and without Airbag Deployments - A Field Data Analysis 1999-01-0633

This study compares the effect of US and European airbag deployments on injury outcomes for belted drivers in frontal crashes. Driver weight, height and seat track position was also examined in relation to those outcomes. This information may help to prioritize and guide the logic for “Smart” airbags.

For the study, only airbag-equipped cars were considered. Two accident databases were used: 1) the weighted and unweighted National Accident Sampling System (NASS-CDS) from the US, calendar years 1995 to 1996, and 2) the unweighted Co-operative Crash Injury Study (CCIS) from the UK, calendar years 1992 to 1998. The parameters investigated were Injury Severity Score (ISS), Equivalent Test Speed (ETS), occupant weight, occupant height and seat location. For US drivers, the injury rate and occurrence were calculated using weighted data, while for UK drivers, the rate and occurrence were obtained using unweighted data. Because the sample size in the two databases was small, the results should only be used for trend analysis.

ETS was an important factor influencing injury rate. For UK deployed cases, all severely injured drivers were involved in a severe crash (ETS > 24 mph), while about 70% of the severely injured US drivers were in crashes with an ETS > 18 mph. In the US, 6 out of 47 deployed cases involving a severely injured (ISS > 12) driver occurred in a low speed accident (ETS < 14 mph). There were no severely injured US drivers in low-speed crashes without an airbag deployment. The rate to be severely injured was thus higher for deployed than undeployed cases at ETS < 14 mph. In the UK, there were no unde-ployed cases in which the driver was severely injured. Although this study does not include an analysis of injury causation, this suggests that minimizing airbag deployments at an ETS < 14 mph would be beneficial for the US market.

The effect of weight, height, and seat location was analyzed for belted drivers involved in a low to moderate crash severity (ETS < 24 mph). Using US deployed data, drivers weighing less than 55 kg had the highest rate to be severely injured. However, more than 50% of US and UK drivers weigh between 56 to 86 kg. US and UK drivers weighing more than 86 kg had the highest rate to be moderately injured when the airbag deployed.

US deployed and undeployed data revealed a trend for a higher moderate injury rate in the < 160 cm height category than other height categories. This finding is also true for UK drivers involved with an airbag deployment. However, short statured (< 160 cm) drivers accounted for less than 8% of the overall belted sample. Seat location was also found to possibly influence US driver injury responses. Though less than 8% of the belted drivers were sitting in the forward seat location, these drivers had the highest rate to be severely injured when the airbag deployed. No drivers sustained an ISS > 12 in the seat forward location when the airbag did not deploy. Since seat location can be used to estimate an occupant’s height, seat location sensing may thus provide important input for US airbag deployment decision logic. Data was not available on seat location in the UK database. Even though the sample size was too small to yield a statistically significant analysis, the trends observed in this study can provide general insight that may be useful in developing future occupant safety countermeasures.