Comparison of US and European belt paths for rearward-facing child restraint systems in frontal-oblique impact sled tests.

OBJECTIVE: To compare the head injury protection offered by rearward-facing child restraint system (CRS) models without a base attached using either the United States (US) or European belt path during frontal-oblique impacts. METHODS: The test buck comprised the Consumer Reports simulated test bench, Federal Motor Vehicle Safety Standards (FMVSS) 213a door surrogate, post-mounted shoulder belt and high-speed camera array. The test buck did not include front-row structures and was rotated relative to the sled deck to represent frontal-oblique far-side (30°) and near-side (30° and 60°) impacts. The 12-month-old Child Restraint/Air Bag Interaction (CRABI-12) anthropomorphic test device (ATD) was seated in one of two rearward-facing infant CRS models without a base attached using either the US or European belt path. A total of 12 sled tests were performed using the FMVSS 213 frontal impact crash pulse (48 km/h, 23 g). Peak forward excursion of the CRS, peak lateral excursion of the ATD head, head injury criterion 15 ms (HIC15) and peak linear accelerations 3 ms clip (PLA3) of the head and chest of the ATD were compared across tests and related to belt path. Head and chest injury metrics were compared to injury assessment reference value (IARVs): HIC15, 390; head PLA3, 80 g; chest PLA3, 60 g. RESULTS: For both CRS models in 30° far- and near-side impact tests, the US belt path had higher head injury metrics compared to the European belt path. For both CRS models in 60° near-side impacts, head and chest injury metrics were greater for the European belt path compared to the US belt path. Head and chest injury metrics were typically below IARVs in 30° far- and near-side impact tests, but IARVs were exceeded in 60° near-side impact tests. For all impacts, CRS models attached using the US belt path underwent substantially greater peak forward excursions compared to the European belt path. CRS models attached using the European belt path in the in 60° impacts had the lowest peak forward excursions. For 30° far-side impacts, peak lateral excursion of the ATD head was greater for CRS models attached using the European belt path compared to the US belt path. CONCLUSIONS: The belt path attachment method of rearward-facing infant CRS models installed without a base influenced pediatric occupant kinematics and injury metrics in frontal-oblique impacts. The European belt path reduced head injury metrics relative to the US belt path for 30° impacts, likely due to reduced forward excursion, but resulted in greater head and chest injury metrics in 60° impacts where increased lateral loading likely exacerbated outboard yaw motion of the CRS into the door surrogate. Conversely, the US belt path produced substantially greater forward excursions that may potentially lead to interaction with front-row vehicle structures, suggesting that head injury metrics were likely underestimated in the current study.