Labels, instructions and features of convertible Child Restraint Systems (CRS): evaluating their effects on CRS installation errors

摘要

This report documents a study of how CRS features, labels, and instructions contribute to CRS installation errors.Task 1A focused on assessing different physical features of 16 convertible CRS, while Task 1B evaluated baseline andmodified versions of labels and instructions for two CRS models. For each phase of testing, 32 subjects were recruitedbased on their education level (high or low) and experience with installing CRS (none or experienced). Each subject wasasked to perform four child restraint installations in a 2006 Pontiac G6 sedan. An 18-month-old CRABI anthropometric testdevice (ATD) weighing 25 lb was used for all installations. Each subject installed two CRS forward-facing (FF), one withLATCH and one with seatbelt, and two CRS rear-facing (RF), one with LATCH and one with the seatbelt. For Task 1A,each subject installed four of the sixteen convertible CRS. For Task 1B, each subject installed a Graco ComfortSport andEvenflo Titan twice, where each CRS had one of eight alternate instruction manuals and one of eight alternate labelconditions. After each installation, the experimenter evaluated 42 factors for each installation, such as choice of belt routingpath, tightness of installation, and harness snugness.Analyses used linear mixed models to identify CRS installation outcomes associated with CRS features or label/ instructiontype. LATCH connector type, LATCH belt adjustor type, and the presence of belt lockoffs are associated with the tightnessof the CRS installation. The type of harness shoulder height adjuster is associated with the rate of achieving a snug harness.Correct tether use is associated with the tether storage method. In general, subject assessments of the ease of use of CRSfeatures are not highly correlated with the quality of their installation, suggesting a need for feedback with incorrectinstallations.The results of testing alternative labels and instructions indicate that no alternative condition significantly improved CRSinstallation compared to baseline conditions across all potential installation errors that were evaluated. An unintendedconsequence of using “combined” labels (incorporating all of the variations recommended by human factors experts thatwere tested individually in other conditions) is that subjects were less likely to use the CRS manual. The most promisingalternative manual is a video version. Neither the labels nor manuals with improved graphics showed substantial benefitcompared to baseline, even though graphics-based manuals and labels score well using the ISO and NHTSA ease-of-userating system. The effects of varying labels and manuals on installation error are small compared to the effects of differentCRS designs.The data from this study provide quantitative assessments of some CRS features that are associated with reductions in CRSinstallation errors. This information can be used to update the NHTSA CRS ease-of-use rating system to account forrecently developed CRS features. Based on human factors recommendations, suggestions are made for assessing “clear”labels and instructions and modifying FMVSS 213 requirements to facilitate clearer labels and instructions.