Analysis of Seat Belt Positioning in Recent NCAP Crash Tests 2013-01-0460
The objective of this study was to analyze the position of the shoulder belt and adjustable upper anchorage (AUA) relative to the occupant in recent (2011-2012) NHTSA NCAP frontal crash tests. Since 2011, certain changes have been made in the NCAP test procedure. These changes include different Hybrid III occupant sizes as well as variations in the methods for calculating injury risk. One of the most significant changes has to do with thoracic injury risk calculation which was previously associated with chest acceleration and is now based on chest deflection as the measurable parameter. Using the NHTSA NCAP database, as well as other crash test data sources, a comparison was made between the designated upper anchorage position prior to a crash test and the actual position of the belt webbing with respect to the chest deflection measurement potentiometer sub-assembly of the Hybrid III. It was found that virtually all of the recent NCAP tests reported a disparity between the position of the shoulder belt webbing and the location of the chest deflection measurement sub-assembly. Furthermore, the effect of this disparity was analyzed using comparable tests with alternative upper anchorage positions. This data comparison reveals a substantial difference in dummy injury measures depending on how the shoulder belt is placed on an occupant prior to a crash test. Finally, comparisons were made using prior research, SAE recommended practices, and United States government engineering reports to determine the biomechanically proper location of the shoulder belt with respect to the occupant.