Interactions Between Rear-Facing Child Restraint Systems and the Front Row Seatback in Frontal Impact Sled Tests

Principal Investigator: Declan Patton, PhD, Children's Hospital of Philadelphia


This was a continuation of prior CChIPS work looking at rear-facing CRS with a support leg, which is also called a load leg. Our previous work used sled testing to look at CRS with a support leg using a blocker plate in front of the CRS to represent a front row seatback. Using this test setup, we found a reduction in head injury metrics in frontal crashes when support legs were used. The current project studied how rear-facing CRS with a support leg interact with an actual front row seat.


The front row seat was set to three positions. The “touch” position moved the front row seat rearward until it just contacted the rear-facing CRS. The “brace” position translated the front row seat 20 millimeters aftward from the touch position, which simulated a front row passenger moving their seat aftwards so that the CRS was braced against the front row seat. The “gap” position translated the front row seat 50 millimeters forward from the touch position, leaving space between the CRS and the front row seat. We conducted 12 total tests: two CRS models – an infant-only CRS with an 18-month-old ATD and a convertible CRS with a 3-year-old ATD – installed rear-facing in the three positions with and without a support leg.


The 18-month-old ATD in the rear-facing infant CRS had the lowest head injury metrics for the touch and gap conditions. In contrast, the 3-year-old ATD in the rear-facing convertible CRS had the lowest head injury metrics for the brace condition. These results can be attributed to the shape and design of each CRS and how the ATD’s head fits within the CRS. However, because only two CRS models were tested, additional research is needed to understand whether these results are representative of the large variety of CRS  designs available.In addition, we found that the tests with a support leg were associated with significantly lower head acceleration, indicating a lower likelihood of injury when a support leg was used. This supports our previous findings that a support leg reduces head injury metrics.


In the absence of a federal safety standard in the US pertaining to support legs, these results can help CRS manufacturers to establish or refine testing and recommendations. Our findings are also relevant for vehicle manufacturers in terms of front row seat design, specifically the interaction between pediatric occupants and vehicle seats. There may be some avenues to reduce head injury metrics through front row seat design.

ATD Image
An 18-month-old ATD seated in a rear-facing infant CRS with support leg installed in the test buck.


Kristy Arbogast, PhD, Children’s Hospital of Philadelphia; Jalaj Maheshwari, MSE, Children’s Hospital of Philadelphia

IAB Mentors

Jonathon Gondek, Calspan Corporation; Emily Thomas, Consumer Reports; Suzanne Johansson, General Motors Holdings, LLC; Mark LaPlante, Graco Children’s Products Inc.;Jake Mitchell, Graco Children’s Products Inc.; Emily Burton, American Honda Motor Co., Inc.; Jerry Wang, Humanetics Innovative Solutions; Curt Hartenstein, Iron Mountains;Kyle Mason, Iron Mountains; Russ Davidson, Lear Corporation;Steve Gerhart, Nuna Baby Essentials, Inc.; Paul Gaudreau, UPPAbaby; Trevor Deland, Toyota USA; Jennifer Pelky, Toyota USA; Uwe Meissner, Technical Advisor