Estimation of the Effects of Vehicle Size and Mass on Crash-Injury Outcome through Parameterized Probability Manifolds

One way to improve vehicle's fuel economy is to reduce its weight. Reducing weight, however has other consequences. One of these is reduced vehicle size. Almost invariably, lighter vehicles are smaller. Reducing vehicle weight has also been associated with a reduction in occupant protection; the lighter the vehicle, the greater the chance of injury when a crash occurs. For this study, a data-based model is used to evaluate the independent effects of size and weight. This model is constructed using the NASS database and information obtained from NCAP tests. The results indicate that although mass is the dominant factor, size also has an effect; some of the observed reduction in safety benefits associated with mass reduction is actually an effect of size reduction. The model is also used to evaluate the effects of varying stiffness. A counterintuitive finding is that increasing the stiffness of the vehicle to reduce compartmental intrusion in severe impacts may not offer an overall improvement in safety. Finally, the model is used to give insights into the effects of reducing the variance of the mass distribution in the vehicle fleet. This shows that the smaller the mass distribution variance, the lower the injury risk.