Effects of high levels of obesity on driver seat belt fit : final report.

Jones, Monica L. H.; Ebert, Sheila M.; Reed, Matthew P. · 2016 · ROSA P / Center for Advancing Transportation Leadership and Safety (ATLAS Center)

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Summary

This study investigates the impact of high levels of obesity on driver seat belt fit, addressing a gap in previous research that had not measured individuals with a Body Mass Index (BMI) ≥ 40 kg/m². Motivated by evidence that obesity increases the risk of severe-to-fatal injuries in crashes due to altered occupant kinematics and poor restraint performance, the researchers aimed to quantify how extreme obesity affects belt routing relative to skeletal structures. Specifically, the study sought to determine if higher BMI causes the lap belt to ride higher and further forward off the pelvis, introducing slack that compromises safety. The research involved 52 licensed drivers (26 men and 26 women) with BMIs ranging from 31 to 59 kg/m² (median 38 kg/m²). Participants were tested in a driver workstation mockup equipped with adjustable seats, steering wheels, and pedals to simulate various vehicle packages. The study manipulated seat belt configurations, including lap belt angles (30°, 52°, 75°) and shoulder belt D-ring locations. Researchers used a FARO Arm coordinate digitizer to record three-dimensional locations of body landmarks, such as the anterior-superior iliac spine (ASIS), and the edges of the seat belt webbing. Standard anthropometric measurements were also collected. Statistical analysis, including regression and ANOVA, was used to assess the relationships between BMI, gender, stature, and belt fit metrics. The results demonstrated that higher BMI was the most significant predictor of poor lap belt fit. As BMI increased, the lap belt positioned itself further forward and higher relative to the pelvis. On average, a person with a BMI of 40 placed the belt 118 mm above and 68 mm forward of the ASIS landmarks, compared to mean values of 31 mm and 33 mm for individuals with a BMI of 25 in previous studies. Lap belt webbing length also increased significantly with BMI, with the highest BMI individuals requiring 350 mm more webbing than the lowest BMI participants. Gender and stature also influenced belt fit, with females generally positioning the lap belt higher and requiring more webbing length than males after accounting for stature. Shoulder belt fit was primarily determined by the D-ring location rather than BMI. The findings confirm that severe obesity significantly degrades seat belt fit by routing the belt away from the underlying skeletal structures, which is associated with poorer restraint performance in frontal impacts. Given that approximately 5% of US adults have a BMI ≥ 40 kg/m² and this cohort is growing rapidly, the study concludes that there is a critical need to improve restraint systems and vehicle design to accommodate individuals with high BMI. Current prevention efforts and vehicle packages do not adequately address the vulnerability associated with this population, highlighting a gap in occupant safety research and engineering.

Key finding

Individuals with a BMI of 40 kg/m2 position the lap belt 118 mm above and 68 mm forward of the anterior-superior iliac spine, significantly worse than the 31 mm above and 33 mm forward observed in individuals with a BMI of 25 kg/m2.

Methodology

lab_experiment

Sample size: 52

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