Predictions of AIS3+ Thoracic Risks for Belted Occupants in Full-Engagement, Real-World Frontal Impacts: Sensitivity to Various Theoretical Risk Curves

Abstract

A new, AlS3+ thoracic risk equation based on chest deflection was derived and assessed for drivers subjected to concentrated (belt-like) loading. The new risk equation was derived from analysis of an existing database of post mortem human subjects in controlled, laboratory sled tests. Binary logistic regression analysis was performed on a subset of the data, namely, 25th-75th percentile men (by weight) from 36-65 years old whose thoracic deformation patterns were due to concentrated (belt-like) loading. Other subsets of data had insufficient size to conduct the analysis. The resulting thoracic risk equation was adjusted to predict the AlS3+ thoracic risks for average-aged occupants in frontal crashes (i.e., 30 years old). Biomechanical scaling was used to derive the corresponding relationships for the small female and large male dummies. The new thoracic risk equations and three other sets of existing equations were evaluated as predictors of real-world crash outcomes. Specifically, thoracic risks associated with belt-only drivers in 1985-1997 model year passenger cars were derived via the four different sets of equations. Comparisons were made from two standpoints: (1) point estimates for 48 km/h potentially barrier-like frontal crashes and (2) aggregate risk estimates derived from simulations of full-engagement, non-rollover, tow-away frontal crashes through 56 km/h. In both cases, the new risk equation agreed with field results. Moreover, an existing thoracic risk equation with a commonly held assumption was shown to significantly overstate observed thoracic field risks.