Objective: The primary objective of this work was to examine variations in the level of crash protection provided by different models of high-back booster seats in frontal impact. Secondary objectives included examination of the influence that specific belt positioning features have on the ability of a booster to achieve and maintain good seat belt fit; and the relationship between dummy loads, motion, and belt fit, both statically (pre-impact) and dynamically (during impact).
Methods: Seventeen different models of high-back booster seats were subjected to simulated frontal impacts on a rebound crash sled. The TNO P10 dummy, instrumented to measure head and chest accelerations and targeted to allow head motion tracking, was used in these tests. Three high-speed cameras were used to record dummy motion. Associations between pre-impact seat belt geometry, the dynamic seat belt fit, and dummy response were examined.
Results: Clear variations were observed in the level of protection provided by the booster seats tested. Specifically, there were variations in the ability to provide and maintain good seat belt fit. Only three of the seventeen booster seats provided good sash (shoulder) and lap belt fit during dynamic testing. All seventeen boosters had a "sash guide." Sash guide type did not appear to influence the dynamic belt fit. However, the location of the guide and ultimately where on the shoulder the sash was positioned pre-impact did influence the dynamic sash fit. Anti-submarine clips (ASCs) that work to position the lap belt low on the abdomen were also found to maintain good lap belt fit during the dynamic tests. However, two booster seats without ASCs were also able to maintain good dynamic lap belt fit, although the mechanism of this behavior is less clear. Though there was a relationship between head excursion, head acceleration and the pre-impact static position of the sash belt (shoulder belt), there was no relationship between dummy response and the overall ability of a booster seat to provide and maintain both good sash and lap belt fit.
Conclusions: Booster seats aim to achieve a good seat belt fit for children too small to use the adult seat belt. Variations in dynamic seat belt fit observed among these seventeen commercially available booster seats demonstrate the need for regulatory protocols that incorporate assessment of dynamic seat belt fit. With current technologies, visual examination of the seat belt during dynamic testing is the best method for assessing this performance.