Currently, manufacturers design their vehicles to meet requirements of frontal crash tests that evaluate both belted and unbelted occupants. Now that approximately 90% of occupants use seatbelts, the question arises as to whether the unbelted requirement is warranted, especially if meeting the unbelted requirement would compromise protection for belted occupants. The project research team performed simulations to optimize restraint systems for two vehicles, first while including the unbelted requirement and again without. The restraint systems optimized under these regulatory test conditions were then evaluated under 55 types of frontal crashes that represent a broader range of realistic crashes. Additional analysis of crashes was used to evaluate the baseline risk of injury and what would happen if the unbelted requirement was removed. This study combined computational modeling and crash-data analysis to demonstrate potential for reducing injury risks to belted occupants if the unbelted requirements are eliminated.


Another project used statistical simulations to examine the hypotheses that passenger vehicles meeting European Union (EU) safety standards have similar crashworthiness to United States (US) -regulated vehicles in the US driving environment, and vice versa. The first step involved identifying appropriate databases of US and EU crashes that include in-depth crash information and to harmonize variable definitions and sampling criteria. Logistic regression models of injury risk were constructed for EU-regulated and US-regulated vehicles. The injury risk predictions of the EU model and the US model were each applied to both the US and EU standard crash populations. The results indicate that EU vehicles most likely have a lower risk of injury in front/side impacts, while US vehicles most likely have a lower risk of injury in rollovers. This study has implications for international trade, in that vehicles that meet EU safety requirements may provide a different level of safety than those meeting US safety requirements.