Standardized error severity score (ESS) ratings to quantify risk associated with child restraint system (CRS) and booster seat misuse.

OBJECTIVE: Although numerous research studies have reported high levels of error and misuse of child restraint systems (CRS) and booster seats in experimental and real-world scenarios, conclusions are limited because they provide little information regarding which installation issues pose the highest risk and thus should be targeted for change. Beneficial to legislating bodies and researchers alike would be a standardized, globally relevant assessment of the potential injury risk associated with more common forms of CRS and booster seat misuse, which could be applied with observed error frequency-for example, in car seat clinics or during prototype user testing-to better identify and characterize the installation issues of greatest risk to safety. METHODS: A group of 8 leading world experts in CRS and injury biomechanics, who were members of an international child safety project, estimated the potential injury severity associated with common forms of CRS and booster seat misuse. These injury risk error severity score (ESS) ratings were compiled and compared to scores from previous research that had used a similar procedure but with fewer respondents. To illustrate their application, and as part of a larger study examining CRS and booster seat labeling requirements, the new standardized ESS ratings were applied to objective installation performance data from 26 adult participants who installed a convertible (rear- vs. forward-facing) CRS and booster seat in a vehicle, and a child test dummy in the CRS and booster seat, using labels that only just met minimal regulatory requirements. The outcome measure, the risk priority number (RPN), represented the composite scores of injury risk and observed installation error frequency. RESULTS: Variability within the sample of ESS ratings in the present study was smaller than that generated in previous studies, indicating better agreement among experts on what constituted injury risk. Application of the new standardized ESS ratings to installation performance data revealed several areas of misuse of the CRS/booster seat associated with high potential injury risk. CONCLUSIONS: Collectively, findings indicate that standardized ESS ratings are useful for estimating injury risk potential associated with real-world CRS and booster seat installation errors.

LATCH (Lower Anchors and Tethers for CHildren) usability in school buses and passenger vehicles.

OBJECTIVE: The present study was designed to assess LATCH (Lower Anchors and Tethers for CHildren) usability in both cars and school buses. Despite being designed to make child restraint system (CRS) installation in vehicles easier and with fewer opportunities for misuse, there have been reports that LATCH is not as easy to use, or as effective, as hoped. To date, there have been few systematic or experimental studies evaluating LATCH usability. Further, based on research demonstrating that small children in school buses are not protected from injury in the same manner as larger children, motor vehicle safety regulations now require LATCH anchorages to be installed on a proportion of seats in all school buses, allowing for the installation of CRS. The main objectives of the study were to assess LATCH usability in cars and school buses and to make recommendations to improve its design and labeling. METHODS: Forty-eight paid participants (younger vs. older; experienced vs. not experienced) installed CRS in a car and a school bus using three different types of lower anchorage connectors and top tethers. Dependent measures included time to install and remove the CRS, frequency and seriousness of errors, and subjective usability reports. RESULTS: Surprisingly, many participants were not familiar with the LATCH system and believed that CRS should only be installed using the seat belt. Over 40% of participants did not know where the lower anchorage connectors were located in the car. While installation performance using LATCH was generally satisfactory (all CRS were installed correctly between 70 and 92% of the time), LATCH design improvements in terms of the CRS and both vehicles were identified. CONCLUSIONS: The study results generated a number of recommended design improvements that would improve LATCH usability in cars and school buses. These include: 1) clearly identifying LATCH anchors in both vehicle types by using clear, conspicuous labels or pictograms; 2) making LATCH anchors in all vehicles more accessible; 3) designing LATCH components for CRS that are easy to use correctly, provide adequate feedback to users, and are difficult to misuse; 4) anticipating, and designing to minimize, incompatibility between CRS and vehicles; 5) using maximum seat spacing in school buses for seats equipped with LATCH anchors; and, most importantly, 6) raising awareness of LATCH in the driving public.