Principal Investigator: Jalaj Maheshwari, MSE, Children’s Hospital of Philadelphia
WHAT WAS THE PURPOSE OF THIS PROJECT?
Most standard testing for child safety seats or vehicles is conducted in an ideal configuration – with the ATDs seated upright in a very rigid sitting posture. But real-world data suggests that children don’t sit like that and instead take various postures across a trip for comfort and to engage in numerous activities while riding. These postural changes can alter the seat belt routing, resulting in non-ideal seat belt placement across the child. Further, due to different booster seat designs, the seat belt routing may be further affected. Therefore, it’s important to assess occupant protection in these naturalistic seating postures, specifically how seat belt fit would change in those postures and how booster seats with varying static belt fit could affect dynamic crash performance when the occupant is positioned this way.
HOW WAS THE RESEARCH CONDUCTED?
We positioned the Q6 ATD on two booster seats (each with different static belt fit metrics) in three seating postures: standard reference, leaning forward, and leaning inboard. Prior naturalistic studies have shown that these postures are most observed in children. We collected belt fit metrics such as shoulder belt score (lateral distance between the suprasternale and inboard edge of the shoulder belt), lap belt score (distance in the sagittal plane between the superior edge of the lap belt and the anterior superior iliac spine (ASIS), gap size (3D distance between the shoulder belt and torso), gap length (distance along shoulder belt in gap region), and percentage torso contact (percent of shoulder belt length along the torso that is in contact with the torso). We then performed 12 frontal impact sled tests, recorded kinetic and kinematic measures, and conducted statistical analysis across conditions.
WHAT DID YOU FIND?
Static belt fit does affect dynamic crash test performance. The booster seat with more inboard shoulder belt, more inferior lap belt, and larger gap size had relatively better kinetics and kinematics than the other conditions with greater outboard shoulder belt, superior lap belt, and smaller gap size.
WERE ANY OF THE RESULTS SURPRISING?
Even small differences in static belt fit resulted in statistically significantly better kinematic and kinetic performance. The booster seat with slightly better belt fit had significantly lower head and chest acceleration, HIC15 (an objective measure of head injury severity), neck tensile force, abdominal pressure, and higher ASIS force and moment. Additionally, the better belt fit booster had lower forward head excursion and chest deflection.
WHAT ARE THE INDUSTRY IMPLICATIONS?
These data will help guide booster seat design improvements to provide comprehensive child occupant protection in all types of seating scenarios.
We need to assess the relationship of static belt fit with dynamic sled test performance across a range of belt fit metrics in frontal, oblique, and side impacts. There’s a lot of work to be done that builds from here.
Gretchen Baker, PhD, The Ohio State University; Madeline Griffith, MSE, Children’s Hospital of Philadelphia; Julie Mansfield, PhD, The Ohio State University; Declan Patton, PhD, Children’s Hospital of Philadelphia
Jonathan Gondek, Calspan Corporation; Emily Thomas, Consumer Reports; Suzanne Johansson, General Motors Holdings LLC; Mark LaPlante, Graco Children’s Products Inc.;Marianne LeClaire, Graco Children’s Products Inc.; Susan Mostofizadeh, American Honda Motor Co., Inc.; Bill Lanz, American Honda Motor Co., Inc.; Jerry Wang, Humanetics Innovative Solutions Inc.; Schuyler St. Lawrence, Toyota USA; Uwe Meissner, Technical Advisor