Occupant Safety in Vehicles Equipped with Automated Driving Systems, Part 1: Initial Evaluation of Usability, Stability, and Injury Prediction Capabilities

Lin, Hongnan; Gepner, Bronislaw; Wu, Taotao; Forman, Jason L.; Shaw, Greg; Panzer, Matthew B. · 2020 · ROSA P / United States. Department of Transportation. National Highway Traffic Safety Administration

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Summary

This report evaluates the usability, stability, and injury prediction capabilities of three occupant models—the NHTSA THOR finite element (FE) model, the GHBMC M50-O (detailed), and the GHBMC M50-OS (simplified)—in seating postures enabled by automated driving systems (ADS). As ADS technology advances, occupants may adopt out-of-position postures such as reclined, rotated, or sleeping positions, which challenge current restraint systems designed for upright drivers. The study aimed to determine if existing human body models and anthropomorphic test devices can accurately simulate these non-standard configurations and identify their technical limitations. The researchers conducted approximately 175 full-vehicle finite element simulations using a validated 2012 Toyota Camry model. The simulations involved 56 km/h impacts with a moving deformable barrier at various angles. Occupants were placed in the right front passenger seat across five study categories: varying seat recline angles (25°, 45°, 60°), seat orientation rotations (forward to rear-facing), turned occupant torsos, occupants leaning against belts in a sleep-like posture, and occupants seated far back from the instrument panel. Restraints included front, side, and curtain airbags, along with standard or integrated seat belts. The results highlighted significant usability and stability issues with all three models. The THOR FE model’s pelvis design physically constrained effective recline beyond 40°, and it exhibited instability in certain configurations. Both GHBMC models were too stiff to allow natural gravity settling into reclined positions, requiring substantial computational effort or forced positioning. The GHBMC M50-OS model suffered from negative volume errors in the abdomen during belt loading and lacked continuity constraints between superficial tissue, skeleton, and internal organs, leading to unrealistic soft tissue displacement. Furthermore, the M50-OS model demonstrated a higher propensity for submarining compared to the THOR model, alongside differences in pelvis rotation and lumbar spine flexion. The study concludes that current occupant models have notable limitations for ADS-related safety research. While the modified GHBMC M50-OS showed reasonable stability, its biofidelity issues and tendency toward submarining suggest it may not accurately predict injury risks in reclined postures. The THOR model is limited by its mechanical design, and the detailed GHBMC M50-O is computationally prohibitive for routine use. These findings indicate that existing tools require significant modification or development to effectively evaluate occupant protection in the diverse seating configurations expected in automated vehicles.

Key finding

The THOR FE model's pelvis design constrained maximum recline, while GHBMC models were too stiff for natural gravity settling and the M50-OS model exhibited negative volume errors and lacked tissue continuity constraints.

Methodology

modeling

Provenance

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

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• passenger motion sickness comfort

Information type

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• Empirical Findings: crash risk outcomes