Development and Evaluation of a Belt Restraint System for Small Cars Using Force Limiting

Walsh, Michael J.; Kelleher, Barbara J. · 1979 · ROSA P / United States. Department of Transportation. National Highway Traffic Safety Administration

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Summary

This 1979 report by Calspan Corporation details the development and evaluation of a passive belt restraint system for small cars, specifically designed to manage occupant loads during high-speed frontal impacts. The research was motivated by the National Highway Traffic Safety Administration’s (NHTSA) goal to extend passive occupant protection to smaller vehicles at collision speeds exceeding 48 km/h (30 mph). Standard webbing belts were found to impart injury-producing loads to the upper torso at these higher energy levels. Consequently, the study aimed to create a producible, force-limiting belt system that met Federal Motor Vehicle Safety Standard (FMVSS) 208 injury criteria while incorporating passive deployment and pretensioning capabilities. The methodology combined three-dimensional computer simulations using the Calspan-developed Crash Victim Simulation (CVS III) program with physical sled testing. Researchers utilized a Chrysler L-body (Omni-Horizon) body buck mounted on a 12-inch HYGE sled facility. The restraint system featured energy-absorbing webbing supplied by Takata-Kojyo, capable of limiting forces at 4.4 kN (1000 lbs) or 6.7 kN (1500 lbs), and an energy-managing knee bar to control lower extremity loads. Two types of belt pretensioners—a Repa Pelton wheel device and an FFV linear pyrotechnic device—were evaluated to reduce webbing spool-off. The study tested various Anthropometric Test Devices (ATDs), including 5th percentile female, 50th percentile male, 95th percentile male, and 6-year-old child dummies, at velocities ranging from 54 km/h (34 mph) to 72 km/h (45 mph). The results demonstrated that the force-limited, pretensioned belt system achieved performance evaluation criteria values within FMVSS 208 limits for the 50th percentile male ATD in both driver and right-front passenger positions at 72 km/h and 56 km/h, respectively. Computer simulations were refined to correlate closely with sled data, though the CVS III program proved insufficient for accurately simulating off-size ATDs (6-year-old, 5th percentile, and 95th percentile). A significant finding was that the 6-year-old sized ATD could not be adequately protected by the torso-belt-only system, even with an active lap belt, as FMVSS 208 criteria were exceeded. This indicated a need for specialized restraint designs for child-sized occupants. Additionally, the force-limiting webbing provided clear visual indication of use through fiber breakage. The study concluded that a force-limiting, pretensioned belt system is a viable passive restraint solution for small cars at high impact speeds, provided it is tailored for adult-sized occupants. The integration of pretensioning effectively managed spool-off issues inherent in force-limiting mechanisms. However, the inability to protect 6-year-old occupants highlighted a critical gap in passive restraint technology, necessitating further research into specialized child restraint solutions. The work established a foundational data set for future development of passive systems and validated the use of computer simulations as a tool for trend analysis in restraint system design.

Key finding

The force-limiting belt restraint system met FMVSS 208 injury criteria for the 50th percentile male at 72 km/h but exceeded limits for the six-year-old sized occupant.

Methodology

simulator

Sample size: 40

Provenance

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

Topics

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• seat belt use