Performance of harnessed child restraints on vehicle seats with modified cushion lengths and variable belt geometry

Abstract

The current series of tests was conducted to identify potential negative outcomes on child restraint performance if recommendations to shorten cushion length and use belt geometry optimized for older child occupants would be implemented. Forty frontal impact tests with four different forward-facing child restraints and 47 tests with five different rear-facing child restraints were performed. Some tests were run using the FMVSS No. 213 bench to establish baseline conditions, but most were run using real vehicle seats with the cushion length set to 350 mm, 400 mm, or 450 mm. Lap belt anchorage locations were set to match the FMVSS No. 213 locations or the locations optimized for the 6YO ATD crash test dummies (Hu, Wu, Reed, Klinich, & Cao, 2013). Some tests attached the child restraint using the lower anchors rather than the lap+shoulder belt. Forward-facing tests were run with and without tethers. Under most testing conditions, the child restraints met applicable FMVSS No. 213 requirements and kinematics appeared reasonable. Among the forward-facing tests, two child restraints with a recline foot slipped off the front edge of the seat, but still met relevant head excursion criteria. Among rear-facing tests, one child restraint exceeded the allowable chest acceleration criteria under most conditions. Overall, the results suggest that shortening seat cushion length to provide a better restraint environment for children using the vehicle seat and belt alone would not adversely affect the performance of most child restraints. Modifications to the lap belt anchorages would also not have a substantial adverse effect.