Quantifying CRS Fit in the Vehicle Seat Environment – Focusing on Incompatibilities

Co-Principal Investigators: Amanda Agnew, PhD, The Ohio State University; Julie Bing, MS, The Ohio State University

Below is an executive summary of this project. Please note that this summary describes results and interpretation that may not be final. Final interpretation of results will be in the peer-reviewed literature.

Wide varieties of child restraint systems (CRS) and vehicle interior designs suggest that not every CRS can fit seamlessly into every vehicle. Previous work has identified specific areas of incompatibility between a large portion of CRS and vehicles available on the US market. With these areas of concern identified, more detailed information is now required to support manufacturers’ improvement efforts and to help define priority levels for each potential incompatibility. The long-term objective of this study was to improve fitment between CRS and vehicle models by establishing the frequency, severity, and consequences of various incompatibilities.

At left: Each RF CRS was first installed without any additional items. The yellow line represents the
manufacturer’s level-to-ground line (outside of the target range).
At right: The same CRS re-installed with a rolled towel to correct the angle.

Phase 1 of this study aimed to document a large number of physical CRS installations in vehicles to develop detailed descriptions of problems and further validate methods to predict these problems. To this end, 10 common convertible CRS were installed in the outboard and center positions of 10 common family vehicles. Rear-facing (RF) and forward-facing (FF) modes were evaluated for each CRS, and all were installed using both Lower Anchors and Tethers for Children (LATCH) and seat belt methods. Quantitative and qualitative data were collected from each of the 632 completed installations.

In Phase 2, sled tests were performed to investigate the consequences of common incompatibilities on occupant safety. Frontal sled tests were conducted with RF CRS installed on second-row vehicle seats to determine if performance was affected by:

a) using pool noodles to achieve proper base angle

b) allowing the front edge of the CRS base to “overhang” the front edge of the vehicle

The sled test conditions for the control trial vs. the overhang trial. The spacer in the photo on the right effectively shortened the
seat pan length so that 20 percent of the CRS base was overhanging the front edge of the vehicle seat.
When the spacer was inserted, the vehicle seat was slid backwards an equal amount on its slider track
so that all seat belt anchors were in the same position relative to the new seat bight. 

Overall, installations could be completed according to the manufacturers’ instructions for 98.4 percent of RF CRS installations and 95.9 percent of FF CRS installations.  Three out of the ten RF CRS installed in vehicles demonstrated consistent inability to achieve proper base angle without the use of a rolled towel or pool noodle. This incompatibility was generally well predicted by the previous external evaluations of both CRS and vehicle seat pan angles. Eight frontal sled tests of convertible CRS in RF mode indicated no reduction in performance caused by either pool noodle installations or front edge overhang compared to control trials. Slightly more lateral rotation of the CRS was observed in RF CRS installations with front edge overhang compared to control trials, but all other kinematic and injury values were not significantly different.

The majority of CRS installations could be completed according to manufacturers’ instructions, although some exhibited minor issues or required after-market items to aid in angle alignment. Pilot sled testing did not reveal any major causes for concern regarding pool noodle usage or front edge overhang for one model of RF CRS.

IAB Mentors

Keith Nagelski, Britax Child Safety, Inc.; Eric Dahle, Evenflo Company Inc.; Julie Kleinert, General Motors Holdings LLC; William Conway, Graco Children’s Products Inc.; Drew Kitchens, Graco Children’s Products Inc.; Mark LaPlante, Graco Children’s Products Inc.; Uwe Meissner, Technical Advisor