In 2011 the National Highway Traffic Safety Administration (NHTSA) made changes to the new car assessment program (NCAP) frontal full-width test rating that introduced a chest deflection metric. The dummy seating protocol did not specify routing procedures that consistently control shoulder belt positioning on the dummy. Thus, most NCAP tests were conducted with the D-ring in the full up position, placing the shoulder belt far above the center chest potentiometer, thereby loading the dummy's chest asymmetrically. Previous research conducted with a Dodge Caliber, showed that differences in chest deflection measurement caused by variations in belt routing are not trivial. The NHTSA NCAP test produced a chest deflection of 11.8 mm, corresponding to a risk of serious chest injury for older females of 0.6%. A crash test conducted by the Insurance Institute for Highway Safety (IIHS) under the same conditions but with the belt routed across the deflection potentiometer produced a chest deflection of 34.5 mm, corresponding to a risk of serious chest injury for older females of 44.7%. This indicated a need for a better belt positioning procedure to replace the vehicle body-based D-ring procedure. This improved positioning would ensure that the belt location relative to the chest deflection potentiometer could be more carefully specified and controlled. The objective of this study is to investigate the use of supplementary chest deformation sensors, such as RibEye and IR-TRACCs for identifying belt fitment procedures which provide accurate chest readings by ensuring that the shoulder belt is routed near the dummy's center chest gage. The present study examines in detail the chest deflections observed in the initial series of sled and full vehicle tests with the Dodge Caliber. In addition, the study examines the chest deflections observed in NHTSA and Transport Canada (TC) full frontal tests with dummies containing supplemental chest deformation sensors. The supplementary data took the form of Hybrid III 5th female dummies outfitted with either RibEye sensors or IR-TRACCs and Hybrid III 50th male dummies outfitted with IR-TRACCs. The results indicate greater disparity between the center chest gage measurements and the supplemental RibEye or IR-TRACC readings when the belt routes higher on the dummy's neck, associated with the upper anchorage D-ring in the full up position. Effects of the D-ring positioning are lessened as the seat track is moved from full forward to midtrack for the 5th female dummy. Since the belt routes closer to the center gage, both the center gage and maximum RibEye measurements indicate more deflection than at the full-forward position. Other factors also contribute to these higher peak measurements. For both the 50th male and 5th female right front passenger dummies, when the belt was routed closer to the dummy's design intention at the center gage, the center gage and left side supplemental (RibEye or IR-TRACC) measurements were similar. Additionally, when the belt was placed across the center of the dummy's chest, the supplemental sensors deflected quite uniformly across the chest. Despite the promising test results of these supplemental chest measurement devices, currently, there is no US federal basis for calibrating or interpreting RibEye or IR-TRACC measurements in Hybrid III dummies, so using these devices to relate to injury risk remains problematic. RibEye and IR-TRACC supplemental chest deflection technologies have the potential to better identify belt routings consistent with the design characteristics of the dummy chest and deflection sensor. This knowledge could be used to develop testing and belt placement protocols which support more meaningful and consistent estimates of chest injury risk. This, in turn, would greatly enhance the utility of NCAP programs to drive restraint system changes to further reduce real-world chest injuries.
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