Development of a Surrogate Shoulder Belt Retractor for Sled Testing of Booster Seats

Manary, Miriam A.; Klinich, Kathleen D.; Boyle, Kyle J.; Orton, Nichole R.; Eby, Brian J.; Weir, Quentin · 2019 · ROSA P / United States. Department of Transportation. National Highway Traffic Safety Administration

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Summary

This study addresses the limitations of current Federal Motor Vehicle Safety Standard (FMVSS) 213 testing for booster seats, which utilizes static lap and shoulder belts that fail to replicate the dynamic behavior of vehicle seat belt retractors. Commercial retractors allow for webbing spool-out during crashes, influencing occupant kinematics and potentially reducing submarining risks. The research aimed to develop a reusable, repeatable surrogate shoulder belt retractor that mimics commercial retractor performance—specifically regarding initial tension and spool-out—to enable more realistic sled testing of booster seats without the cost and variability of using new production retractors for each test. Researchers conducted a survey of 20 vehicles to establish performance targets, finding that commercial retractors typically exhibit 25–50 mm of spool-out and 9–18 N of resting tension. Based on these findings, a compact surrogate retractor was developed using a split drum, rotating spindle, and constant force spring to control resistance and tension. Dynamic sled tests were performed using a Hybrid III 6-year-old anthropomorphic test device (ATD) across two series. The tests evaluated four backless booster seats (Graco TurboBooster, Evenflo AMP, Safety 1st Incognito, and BubbleBum) and a no-booster condition. Testing utilized three belt configurations: static belts, production belts from 2011 Ford Explorer and Jeep Cherokee vehicles, and the new surrogate retractor. Tests were conducted on both production vehicle seats and a preliminary FMVSS 213 test bench. MADYMO modeling was also employed to validate test data and analyze the effects of spool-out and anchor positioning on kinematics. The results demonstrated that the surrogate retractor produced kinematics similar to those achieved with production seat belts in a repeatable manner. Data comparisons of head excursion, knee excursion, Head Injury Criterion (HIC), chest acceleration, and shoulder belt loads showed that surrogate retractor responses closely matched production retractor responses, whereas static belts often yielded different kinematic profiles. For instance, the surrogate allowed for forward torso rotation consistent with live retractors. The study also identified test protocol issues, such as shoulder belt misalignment, which led to adjustments in the test bench’s D-ring anchorage. MADYMO models confirmed that increased spool-out and specific anchor positions significantly influenced torso angle and excursion metrics. The significance of this work lies in providing a practical, reusable tool for evaluating booster seat compatibility with real-world vehicle seat belts. By replicating the dynamic characteristics of commercial retractors, the surrogate allows for more accurate assessment of booster designs, potentially leading to improved safety outcomes that account for retractor-induced kinematics. This development supports future revisions to FMVSS 213 testing protocols, ensuring that booster seat evaluations better reflect actual vehicle conditions.

Key finding

The surrogate shoulder belt retractor produced kinematics similar to those achieved with production seat belts in a repeatable manner.

Methodology

simulator

Provenance

The full processing record for this entry. Every stage of this paper's journey through the pipeline is logged — what ran, with which tool and model, how many attempts it took, and when it last completed. Discovered via bulk_ingest_rosap on 2026-05-23 (6 acquisition events logged).

Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.

Topics

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• seat belt use