Occupant Dynamics During Crash Avoidance Maneuvers

Reed, Matthew P.; Ebert, Sheila M.; Jones, Monica H.; Park, Byoung-keon D · 2021 · ROSA P / United States. Department of Transportation. National Highway Traffic Safety Administration

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Summary

This study investigates the kinematics of front-seat occupant heads during abrupt crash avoidance maneuvers, addressing a critical gap in understanding pre-crash occupant dynamics. While crashworthiness standards focus on impact events, the initial posture and position of occupants during evasive maneuvers significantly influence injury risk. The research aims to quantify how factors such as seat position, foot placement, recline angle, seatbelt retractor status, vehicle type, and leaning behaviors affect head excursions during braking, lane changes, and turn-and-brake events. The methodology involved a two-phase test-track study conducted by the University of Michigan Transportation Research Institute. A pilot study with 12 participants assessed head excursions across a sedan, minivan, and pickup truck. This was followed by a full-scale study with 90 participants of varying ages and body sizes, using a passenger sedan and an SUV. Participants underwent five maneuver types: two braking events, right and left lane changes, and a turn-and-brake maneuver. Head center of gravity (CG) trajectories were tracked using a Kinect-based system and 3D head scans. The study manipulated specific conditions, including seat track positions (rear, mid, forward), foot postures (heels vs. soles), seat back angles (23°, 35°, 47°), retractor locking states, and leaning/reaching postures. Functional regression analysis was employed to model head CG trajectories and identify significant predictors of motion. Results from the pilot study indicated slightly smaller forward head excursions in the sedan compared to the minivan and truck, though vehicle kinematics were similar. The full-scale study revealed that occupant head locations varied widely based on initial conditions. For braking maneuvers, forward excursion was significantly influenced by seat position, foot posture, recline angle, and forward leaning. Specifically, sitting further forward, keeping feet on heels, maintaining an upright posture, and leaning forward minimized forward head excursion. Age and stature also played significant roles, with younger, taller individuals exhibiting greater excursions. During lane changes, inboard and outboard excursions were affected by seat position, foot posture, and BMI. Functional regression models successfully generated parametric corridors for head CG trajectories, demonstrating that specific combinations of occupant variables could maximize or minimize head motion. The significance of this work lies in the development of parametric corridors that can tune and validate computational models of occupant responses in pre-crash scenarios. By establishing how initial posture and vehicle dynamics influence head motion, the study provides essential data for improving safety systems, such as pre-tensioners and airbag deployment timing, which rely on accurate predictions of occupant position before impact. The findings underscore that a wide range of head locations can result from abrupt maneuvers, necessitating robust modeling capabilities to ensure occupant safety across diverse populations and driving behaviors.

Key finding

Abrupt vehicle maneuvers produce a wide range of occupant head locations influenced by seat position, recline angle, and leaning behaviors, with forward head excursion being slightly smaller in a passenger car compared to a minivan and pickup truck in the pilot phase.

Methodology

on_road

Sample size: 90

Provenance

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

Topics

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• driver post crash behavior
• evacuation egress

Information type

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• Empirical Findings: behavioral performance data, crash risk outcomes