Properly restraining a child in an automotive seat may require the use of a weight- and size-appropriate Child Restraint System (CRS). Proper installation of the CRS is a critical part of protecting a child during a motor vehicle collision. During a collision, child occupants sometimes exert enough force on the restraint system to generate load marks on the CRS and the vehicle restraint system. These marks are often relied upon by investigators to determine if the child occupant was properly restrained at the time of the collision. This paper is an observational study of the load marks generated from sled testing that was conducted using Hybrid III 3-year-old and 6-year-old Anthropomorphic Test Devices (ATDs). Tests were conducted with various child restraint systems that were installed in accordance with the manufacturer's recommendations as well as installed improperly. Additional tests were conducted with the ATDs without the use of a CRS. Load mark comparisons were made with respect to test severity.
The vehicle restraint systems and CRSs used in all tests showed load marks as a result of the sled tests. Identifying the location of specific marks on the vehicle restraint systems was critical in determining how tightly the CRSs or ATDs were attached to the vehicle seats during the tests. Of all the objects that interacted with the vehicle restraint webbing during the tests, the latch plate was found to create marks on the vehicle restraint webbing that most closely matched its pre-test position. Thus, in this study a positively identified latch plate mark on the restraint webbing enabled a reasonable estimation of how the lap portion of the vehicle restraint was routed and how tightly the CRS was installed. However, this phenomenon may be specific to the particular tests contained in this study and should not be taken into broader context.
At higher test severities, more stress marks and fractures to polymer components of the CRSs were observed, and the marks found on the load-bearing surfaces of the CRSs were generally more pronounced. The amount of stress whitening that appeared on the CRSs was not readily apparent on the lower-severity sled tests and no parametric relationship was drawn. However, it was concluded that as the collision severity increases, so does the propensity for stress whitening. For this reason, the presence of stress whitening in specific areas on the CRSs in these tests should be viewed as a means to potentially support the involvement of a CRS in a collision and not as a means to quantify accident severity.