Shoulder Belt Interaction for Booster-Seated ATDs

Principal Investigator: John H. Bolte IV, PhD, The Ohio State University


This project built upon previous CChIPS work where we developed new ways to measure seat belt fit for children. We found a lack of contact between the shoulder belt and the lower torso on some booster seats, which we call belt gap, and we observed differences in belt gap among various booster seat designs. This study took the next step to investigate how variation in belt gap relates to differences in crash outcomes. To do this, we tested three ATDs on six different booster seats, which varied in their initial belt gap, in two crash scenarios: frontal and 15 degrees from the frontal direction. We primarily looked at the following outcomes: head acceleration and displacement, chest acceleration and deflection, axial shoulder rotation, axial thoracic spine rotation, and lumbar spine moments.


We found generally similar results across the six booster seats in terms of head and chest metrics. However, the ATDs on boosters which had less initial contact between the shoulder belt and lower torso tended to rotate more around their spine, particularly in the lumbar area. We also saw more rotation in the shoulders and thoracic spine for the ATDs restrained in these booster seats. This increase in spinal and shoulder rotation may suggest an increased risk of the seat belt slipping off the shoulder. This trend was observed in both frontal and oblique crash directions.


This research can be applied to other scenarios of occupant protection, such as adult occupants restrained by three-point seat belts. The more we understand the relationships between initial fit of the seat belt, posture, and how occupants respond during a crash, crash outcomes will improve for all occupants.


In follow-up work, we hope to fully tease out the individual influences of each variable (such as initial belt gap and the amount of boost provided by the booster seat) by conducting either additional physical testing (with more seats) or using computational models (simulations) with a simplified booster scenario and examine the effect as each variable is modified parametrically.

Lumbar Chart
This graph shows the lumbar spine movement about the vertical axis (MZ) over time for the LODC 10-year-old for frontal sled tests (left) and 15° oblique (second from left) sled tests and the lumbar spine movement about the vertical axis (MZ) over time for the Q -series 10-year-old ATDs for frontal sled tests (second from right) and 15° oblique sled tests (right). Booster seats with smaller initial belt gap are represented in dashes lines, while larger gap booster seats are represented in solid lines. Booster seats included those with backs (HB), backless (LB), and low-profile (Low).


Gretchen Baker, PhD, The Ohio State University; Julie Mansfield, PhD, The Ohio State University

IAB Mentors

Jonathan Gondek, Calspan Corporation; Michael Kulig, Calspan Corporation; Jennifer Stockburger, Consumer Reports;Emily Thomas, Consumer Reports; Amanda Taylor, Federal Aviation Administration; Josh Gazaway, Graco Children’s Products Inc.; Mark LaPlante, Graco Children’s Products Inc.;Marianne LeClaire, Graco Children’s Products Inc.; Nick Reaves, Graco Children’s Products, Inc.; Kyle Mason, Iron Mountains;Bill Lanz, American Honda Motor Co., Inc.; Jerry Wang, Humanetics Innovative Solutions Inc.; Nick Rydberg, Minnesota HealthSolutions; Jason Stammen, National Highway Traffic Safety Administration; Steve Gerhart, Nuna Baby Essentials, Inc.;Schuyler St. Lawrence, Toyota USA; Paul Gaudreau, UPPAbaby;Uwe Meissner, Technical Advisor