Estimating the Injury-Reducing Benefits of Ejection-Mitigating Glazing
The objective of NHTSA's Advanced Glazing Project was to determine if advanced ejection-mitigating glazing in passenger cars, light trucks, and vans would result in substantial benefits in terms of fatality and injury reductions. Before recommending whether or not advanced glazing should be installed in vehicles in the future, the benefits of ejection prevention have to be assessed via a cost-benefit analysis. This report contributes to this analysis by providing statistical estimates of the relative risk of fatality and injury for ejected occupants of motor vehicles compared to non-ejected occupants and the reduction in fatalities and injuries at different severity levels if ejection were eliminated. The analysis uses state files maintained by the National Center for Statistics and Analysis (NCSA). State data files are records of police accident reports and comprise an extensive collection of crash data. The files are obtained by NCSA each year for analysis purposes. The analysis uses the double-pair comparison methodology to compare the injury rates on various severity levels among the ejected and the non-ejected vehicle occupants. The fractional reductions in fatalities and incapacitating injuries due to ejection prevention are calculated. The relative risk of fatality is reduced by 72% for drivers and 68% for front seat passengers when ejection is eliminated. The relative risk of incapacitating injury is reduced by 58% for drivers and 49% for front seat passengers when ejection is eliminated. Analysis by crash type shows the greatest benefits occur in rollover crashes; analysis by vehicle type shows particularly large benefits for light trucks.