Evaluation of Side Impacts with a Frontal Component for Children in Child Restraint Systems (Multiple Year)

Principal Investigator: Kristy Arbogast, PhD, The Children’s Hospital of Philadelphia  

Year 1: 2014-2015

Image of a sled test showing the FF CRS rotating and tipping towards 
the impact direction, facilitating the ATD head to rotate around the FF CRS side wing.

 

This testing illustrated relevant side-impact crash circumstances where side wings do not provide the desired head containment for a 3-year-old ATD seated far-side or center in a FF CRS. In a center or far-side seating configuration, the absence of a door structure immediately adjacent to the CRS may allow the rotation and tipping of the FF CRS towards the impact side and the roll-out of the head around the side wing structure. Results suggest other prevention measures, in the form of alternative side-impact structure design, FF CRS vehicle attachment, or a combination of safety technology provided by both the vehicle and the FF CRS and the vehicle, may be necessary to protect children in oblique side impact crashes.Side-impact collisions are the second most common crash mode, accounting for 26 percent of fatal crashes for all occupants, and 40 percent of fatalities to children between 0 and 8 years of age. As such, the National Highway Traffic Safety Administration has identified child restraint systems (CRS) protection in a near-side configuration as a safety priority.

Few studies have examined the injury potential to children in side-impact crashes in positions other than the near-side position, such as center seating locations, because they are generally considered safest for the pediatric occupant. For the center- or far-side seated CRS in particular, the potential of CRS to yaw or roll into intruding vehicle components (especially in small-size vehicles) has not been addressed. This line of research is intended to spur development of safety improvements for children in side impacts and is in alignment with recent efforts to meet the safety needs of adults seated in front row positions, during side impacts that are far side to the occupant.

This project aimed to quantify the kinematics and injury potential for anthropomorphic test devices (ATDs) representing a 3-year-old occupant in a far- or center- seated position in an oblique side-impact crash. The project test series examined the influence of side-impact protection features, such as side wings, of a forward-facing CRS (FF CRS), vehicle seat type, and tether routing.

Sled tests were conducted utilizing a Q3s dummy positioned in a FF CRS with large side wings that were removed. The CRS were attached via Lower Anchors and Tethers for Children (LATCH) on two different vehicle seat fixtures – a small SUV rear bench seat with a fixed head restraint, and a minivan rear bucket seat with an adjustable head restraint. The vehicle seats were secured to the sled at 20 degrees from lateral.

Results indicated the side wings have little influence on head excursions and ATD response. Researchers observed primary differences in head response between the two vehicle seat fixtures due to the vehicle seat head restraint design. The bench seat integrated head restraint forced the top tether to be routed over the head restraint. Due to the lateral crash forces, the tether moved laterally off the head restraint reducing webbing tension and increasing head excursion (477 mm median). In contrast, when the tether was routed under the bucket seat’s adjustable head restraint, it maintained a tight attachment and helped control head excursion (393 mm median).

 

Year 2: 2015-2016 

Recent advances in child occupant protection have focused on mitigating fatalities and injuries to children in child restraint systems (CRS) in side-impact or oblique crashes. Although those in near-side seating positions have the highest injury and fatality risk in side-impact scenarios, injuries still occur to occupants seated center or far-side. For these occupants, the most common body region of injury is the head and neck, most frequently caused by head contact with the vehicle interior.

In the first year of this line of study, researchers observed the far-side seated forward-facing (FF) CRS yaw and roll in the oblique impact mode, leading to substantial head excursion of the anthropomorphic test device (ATD), or crash test dummy. This excursion was of the magnitude to lead to potential impact with a vehicle’s intruding components during a side-impact crash. The tests also suggested the tether can provide value in mitigating head excursion and pointed to the need for a more detailed look at the role of the tether.  Based on the Year 1 findings, an extension of this work for a second year used a series of sled tests to explore the role of the tether and intrusion on the kinematics and injury potential of a 3-year-old occupant seated in the center seat in oblique side impacts.

Sled tests were conducted utilizing a Q3s ATD positioned in a FF CRS. CRS were attached to a rear seat from a small SUV via Lower Anchors and Tethers for Children (LATCH) flexible webbing in the center seating position; tests were conducted with and without the tether. The vehicle seat was secured to the sled at both 30 and 10 degrees from pure lateral, with a simulated intruded door secured left of the CRS – on the near side of the crash. 3D motion cameras collected ATD head excursion data, and head accelerations; head rotational velocities; neck loads, as well as webbing and tether loads.

All tests without a tether resulted in head to door contact, with the head rolling out of the FF CRS’s side wings and making contact with the intruded door halfway between top of door and the top of armrest.  The tether reduced excursion and head injury values, indicating its importance for potentially preventing injury in side impacts to children seated center or far-side. In addition to elevated head injury metrics, neck injury metrics were above existing thresholds. 

These results point to the need for further research examining potential CRS attachment design and vehicle interior protection countermeasures to limit head and neck injury, including ways to better contain the head in oblique crashes. Additional padding or inflatable curtains below the vehicle’s window sill also may help better protect small occupants and children.

 

High speed video frame at maximum head excursion, for the FF CRS tested in the untethered condition. 
Note CRS yawing and tipping, and ATD lateral excursion and head impact with the simulated intruded door.

 

Project Team Members:
Hans W. Hauschild, MS, Medical College of Wisconsin (Y1, Y2); Bruce Kaufmann, MD,Children’s Hospital of Wisconsin & Medical College of Wisconsin (Y1, Y2); Matthew R. Maltese, PhD, The Children’s Hospital of Philadelphia (Y1, Y2); Frank A. Pintar, PhD, Medical College of Wisconsin (Y1, Y2); Narayan Yoganandan, PhD, Medical College of Wisconsin (Y1, Y2) 

Students:
John R. Humm, Medical College of Wisconsin (Y1, Y2); Paul Gromowski, MS, Medical College of Wisconsin (Y1).

IAB Mentors:
Eric Dahle,Evenflo Company Inc. (Y1,Y2); Audrey Eagle,FCA US LLC (Y1,Y2)Julie Kleinert, General Motors Holdings LLC (Y1,Y2); Mark LaPlante, Graco Children’s Products Inc. (Y1,Y2); Jerry Wang, Humanetics Innovative Solutions Inc. (Y1,Y2); Hiromasa Tanji, TK Holdings Inc. (Y1,Y2); Schuyler St. Lawrence, Toyota USA (Y1,Y2); Barbara Birkenshaw, Volkswagen Group of America (Y2); Uwe Meissner, Technical Advisor (Y2); Keith Nagelski, Britax Child Safety, Inc. (Y2); Rodney Rudd, National Highway Traffic Safety Administration (Y2); Mike Kulig, Calspan Corporation (Y1); Agnes Kim, Ford Motor Company (Y1); 

About This Center

This Center is made possible through a grant from the National Science Foundation (NSF) which unites CHOP, University of Pennsylvania, and The Ohio State University researchers with R&D leaders in the automotive and insurance industries to translate research findings into tangible innovations in safety technology and public education programs.

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