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Effects of vehicle features on CRS installation errors

This report documents a study of how vehicle features contribute to CRS installation errors. Thirty-two subjects were recruited based on their education level (low or high) and experience with installing CRS (none or experienced). Each subject was asked to perform four child restraint installations in three vehicles. Each subject first performed a CRS installation with a seatbelt in one vehicle, followed by three CRS installations using LATCH, one in each of three vehicles. One child restraint with a hook-on LATCH connector and one with a push-on LATCH connector were used. All installations were forward-facing, using an 18-month-old CRABI anthropomorphic test device (ATD). Six vehicles were used in testing, with half of subjects testing with each vehicle. Conditions were selected to provide a range of LATCH locations (visible, above seating surface, buried in bight), buckle stalk types (webbing vs. rigid), and tether locations (package shelf vs. seatback). After each installation, the experimenter evaluated 28 factors for each installation (such as tightness of installation, tether tightness, and LATCH belt attached correctly). Analyses used linear mixed models to identify the CRS installation outcomes associated with vehicle features. For LATCH installations, vehicles requiring higher forces to attach connectors to lower anchorages were more likely to be attached incorrectly. Vehicle seats with a bightline waterfall (which places the lower anchorage above the seating surface) increased rates of tight CRS installation for both seatbelt and LATCH installs. Seatbelt installations were tight (and locked) more frequently when the buckle stalk was located close to the bight rather than further forward. Subjects used the tether correctly in 30% of installations. Subjects used the tether more frequently during LATCH installations compared to seatbelt installations. The tether was used more frequently in sedans...

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