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

Some child restraint systems (CRS) have built-in tensioning features, such as a door or clasp that closes over the seat belt, that apply tension to the belt to achieve a snug installation. This study aims to quantify how much tension these features produce on the belt to ensure consumers can use the features correctly and that the tensions they produce are similar to current FMVSS 213 test guidelines.

WHAT WAS THE PURPOSE OF THIS PROJECT?

Some CRS manufacturers are introducing seat belt lock-off or tensioning features designed to help consumers achieve tighter installations. Different designs appear to produce different levels of seat belt tension, although this has never been quantified across models. It is also not clear how consumers are interacting with these features or if they can use them correctly.

HOW WAS THE RESEARCH CONDUCTED?

We used an instrumented vehicle seat with a seat belt load cell to measure the amount of tension produced on the belt. Researchers installed 29 different CRSs several times each, producing sequentially increasing tension levels on the belt. Up to 70 installations were completed for each CRS for a total of over 1,600 installations.

Next, 30 adult volunteer participants each installed four different CRSs that had different types of lock-off/tensioning features or no additional features (i.e., baseline design). Following installation, the amount of seat belt tension was measured and any errors were recorded. We compared the volunteer participants’ seat belt tension levels to both the range of values obtained by the researchers and the FMVSS 213 target ranges.

WHAT DID YOU FIND?

We found distinct differences among tension feature designs across CRS models: some added no additional tension while others added upwards of 250 N of additional tension to the installations. For the volunteer tests, we observed improvements in belt tension (within the desired FMVSS 213 range) for CRS models with features designed to add tension to the belt.

The lock-off only model was effective in locking the belt but did not improve overall belt tension levels. We also observed that the belt lock-off/tensioning features introduced some belt routing errors which were not present in the baseline CRS installations.

WHAT ARE THE INDUSTRY IMPLICATIONS?

Our results show that lock-off/tensioning features have the potential to help consumers perform snug, properly locked installations. Manufacturers should be mindful of how the instructions for these features are communicated to consumers. Clear labeling on the CRS and intuitive belt paths may help prevent caregivers from making belt-routing errors in these types of CRS.

The figure shows the final belt tensions produced during installations completed by 30 volunteer participants. The lock-off designs which produce additional tension on the belt (pink and light blue) resulted in significantly tighter installations compared to the non-tensioning lock-off (green) or the baseline CRS without lock-off (dark blue).

IAB Mentors

Jonathon Gondek, Calspan Corporation; Daniel Wells, Calspan Corporation; 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.; Curt Hartenstine, Iron Mountains; Kyle Mason, Iron Mountains; Nick Rydberg, Minnesota HealthSolutions; Erin Hutter, National Highway Traffic Safety Administration; Steve Gerhart, Nuna Baby Essentials, Inc.; Anita Sabapathy, UPPAbaby