Examination of Current MASH Occupant Compartment Intrusion Limits Using Real-World Crash Data

Abstract

Full-scale crash testing is used to assess the performance of roadside hardware devices, such as traffic barriers, via Manual for Assessing Safety Hardware (MASH) procedures. MASH procedures include comparing posttest vehicle occupant compartment deformations in specified vehicle areas with associated intrusion threshold values. Unfortunately, little is known about how MASH intrusion limits relate to real-world crash occupant injury. This study provided an examination of current MASH occupant compartment intrusion limits using real-world, in-depth crashes occurring from year 2000 through 2015. Data for a total of 55,292 crash-exposed occupants were available, representing nearly 26 million crash-exposed occupants. Binary logistic regression models were developed to predict occupant injury at various severity levels using available MASH intrusion thresholds and controlling for potentially confounding factors such as belt use, vehicle type, object struck, posted speed limit, occupant age, and gender. The current MASH intrusion limits in aggregate were found to be strong predictors of maximum occupant injury. Occupants adjacent to one intrusion in excess of the current MASH thresholds were found to be approximately 10 times more likely to be injured. Investigation of intrusion in specific vehicle areas suggested that toe pan intrusion has the largest influence on occupant injury followed by the windshield, A/B pillar, and floor pan areas, but more intrusion cases in different areas are needed to confirm these findings. A descriptive analysis of the injuries suggested that intrusions in different vehicle areas do result in differences in the occupant body regions injured.