Principal Investigator: Julie Mansfield, PhD, The Ohio State University

Comfort is one of the leading factors in booster selection for both adult consumers and child occupants. The goal of this study is to determine how specific booster seat features, including seat pan geometry (booster height and length) and the inclusion of armrests, influence occupant comfort in belt-positioning booster seats. This will be achieved through an analysis of comfort quantification methods and occupant posture and behavior under different booster conditions.

WHAT WAS THE PURPOSE OF THIS PROJECT?

As comfort is one of the leading factors in booster seat selection, this project investigated different design features of booster seats that may influence the way children sit. We were particularly interested in the presence of armrests and the height or overall profile of the booster and these features’ specific influences on the behaviors of children over a 30 minute time period, which has not previously been investigated in a laboratory setting.

HOW WAS THE RESEARCH CONDUCTED?

This study included 30 children between the ages of 5 and 12. Each participant sat in two different seating configurations for 30 minutes each, resulting in a total of 60 trials over five different conditions (high or low profile booster, armrests or no armrests, or baseline).

We analyzed video footage of children’s behavior and measured how many times they moved or fidgeted in the booster, which is a quantifiable comfort metric called the Discomfort Avoidance Behavior (DAB) rate. We used a pressure mat along the seat surface to quantify shifts in each child’s center of force (COF) along with wireless motion capture sensors to evaluate posture changes. We also gave surveys to children and their caregivers to understand their perception of the comfort of the child.

WHAT DID YOU FIND AND WAS ANYTHING SURPRISING?

The most surprising finding was the consistent outcome between the different booster types. While our study subjects varied greatly in terms of height, weight, and maturity level, all children tended to slide their hips forward over time and rotate their pelvises backwards, trending more toward a slouched posture over 30 minutes. Our assumption is that this was done to improve comfort, considering the comfort scores in their surveys didn’t change over the 30 minutes. We did not find any evidence suggesting the armrests influenced comfort levels.

HOW ARE THESE RESULTS APPLICABLE TO INDUSTRY MEMBERS?

These results indicate that booster selection goes beyond height and weight requirements; the maturity and behavior of the child can and should influence restraint choice to ensure optimal safety. It’s also interesting for industry members to know we can quantify children’s postures in boosters and use that information in further research or design improvements to try and mitigate the slouched posture we observed.

Average relative center of force (COF) position for each seating configuration. Time zero represents the upright, ideal, reference posture of each child. Positive values indicate the COF moving forward on the seat surface, indicative of slouching.

Student

Rosalie Connell, BS, The Ohio State University

IAB Mentors

Emily Thomas, Consumer Reports; Suzanne Johansson, General Motors Holdings LLC; James Fitzpatrick, Graco Children’s Products Inc.; Mark LaPlante, Graco Children’s Products Inc.; Joseph Webb, Graco Children’s Products Inc.; Bill Lanz, American Honda Motor Co., Inc.; Susan Mostofizadeh, American Honda Motor Co., Inc.; Kyle Mason, Iron Mountains; Russ Davidson, Lear Corporation; Wu Pan Zagorski, Lear Corporation; Nick Rydberg, Minnesota HealthSolutions; Steve Gerhart, Nuna Baby Essentials, Inc.; Anita Sabapathy, UPPAbaby; Uwe Meissner, Technical Advisor