Assessment of 3 and 6-Year-Old Neck Injury Criteria Based on Field Investigation, Modeling, and Sled Testing

The intent of this study was to compare the neck responses measured from the Hybrid III 3 and 6-year-old ATDs in laboratory testing to injuries sustained by three children in a field crash and investigate the appropriateness of recommended in-position neck injury assessment reference values (IARVs), and the regulated out-of-position (OOP) IARVs specified in FMVSS 208 for the Hybrid III 3 and 6-year-old ATDs. This paper principally reports on apparent artifacts associated with the Hybrid III 3 and 6-year-old ATDs, which complicated investigating the appropriateness of the in-position and out-of-position neck IARVs. In tests using 3-point belt restraints, these apparent artifacts included: 1) High neck extension moments, which produced the peak Nij values, without significant observed relative head-to-neck motion, 2) Neck tension forces well in excess of the IARVs that occurred when the ATD's chin contacted the chest. Because humanlike kinematics and force deflection properties for belt restrained chin-to-chest contact have not been defined, and ATD force deflection criteria are not specified for chin-to-chest contact; the biofidelity of the neck data measured by the ATD during chin-to-chest contact is doubtful. This paper also compares the measured neck injury criteria with 3 and 6-year-old Hybrid III ATDs to the neck injuries sustained by the three children in a previously reported frontal crash. To the extent the test environment simulated the field crash, the out-of-position neck tension IARVs seemed consistent with the injuries sustained by the 3 and 6-year-old children who were in 3-point restraints, but had placed the shoulder belts behind their backs. Excluding neck tension measurements during chin-to-chest contact, the neck tensions measured in the lap/shoulder belted sled tests seemed consistent with the injuries sustained by the lap/shoulder belted 7-year-old child in the field crash. While the Hybrid III 3 and 6-year-old ATDs are the best available tools for assessing child neck injury potential, judgment is needed in interpreting the neck data from tests with belt restraint systems. It is inappropriate to only consider the peak neck measurements without examining the events surrounding those peak values.