Kinematics of Rear Seat Child Occupants in Small Overlap Crashes

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

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.

A post-test photo from the full vehicle small overlap crash testing (photo courtesy of the Insurance Institute for Highway Safety).

Small overlap crashes occur when the primary crash damage comes from a frontal crash but the damage is outside the longitudinal structures of the vehicle. These types of crashes have received recent interest as a crash dynamic that results in high likelihood of injury to both drivers and passengers. Over the past several years, the National Highway Traffic Safety Administration (NHTSA) and the Insurance Institute for Highway Safety (IIHS) have developed extensive test programs to study this crash dynamic, finding significant lateral motion of the vehicle and, therefore, the driver. However, there has been no research into the kinematics of rear seat occupants for this type of crash. Therefore, this study sought to understand injury risks for rear-seated occupants in small overlap crashes through field data analysis and full-scale crash testing.

Using data from NHTSA’s National Automotive Sampling System – Crashworthiness Data System (NASS-CDS) from 2000-2010, injury risk for rear seat occupants in small overlap crashes was calculated. Results suggest that rear seat occupants may be at higher risk in this crash dynamic than front seat occupants – a finding at odds with the conventional understanding that the rear seat has increased protection for its occupants. In addition, head injuries were the most common significant injury sustained by young children.

The second phase of this project explored the kinematics of the rear seat occupant in small overlap crashes in partnership with IIHS through a full-scale crash test of a mid-size sedan. The IIHS small overlap test protocol consists of a moving vehicle striking a rigid, stationary barrier at 64 km/h, with a 25 percent overlap of vehicle and the barrier. In the left rear seat was a lap-shoulder belt restrained Hybrid III 5th percentile female anthropomorphic test device (ATD) and a backless booster seated Hybrid III 6-year-old in the right rear. During the crash, the 5th percentile female submarined as slack was introduced into the lap belt through deformation of the seat belt anchors. However, even with the submarining, the ATD’s head contacted the vehicle door just below the windowsill. The 6-year-old moved substantially inboard, particularly on rebound, suggesting the restraint system was not fully able to control the kinematics.

The kinematics of the 5th percentile female were further explored through computational modeling. By positioning this occupant in a realistic position and posture, the simulation demonstrated contact between the ATD head and the intruding vehicle door, providing support for the injury causation scenario observed in real world crashes.

This study provides the first in-depth examination of the rear-seat passenger environment in small overlap crashes and is an important step toward understanding rear seat head injury mitigation. By quantifying the injury risk, vehicle dynamics and associated kinematics of rear seat child occupants in this crash dynamic, manufacturers now have a better understanding of the circumstances that lead to a substantial proportion of serious head injuries and fatalities.

Project Team Members

Caitlin Locey, BS, Children’s Hospital of Philadelphia; Rachel Hammond, MS, Children’s Hospital of Philadelphia; Aditya Belwadi, PhD, Children’s Hospital of Philadelphia; Chris Sherwood, MS, Insurance Institute for Highway Safety

IAB Mentors

Eric Dahle, Evenflo Company Inc.; Julie Kleinert, General Motors Holdings LLC; Rodney Rudd, National Highway Traffic Safety Administration; John Combest, Nissan Technical Center North America Inc.; Kazuo Higuchi, TK Holdings Inc.; Schuyler St. Lawrence, Toyota Motor North America Inc.; Richard Bandstra, Volkswagen Group of America

Publication References

Annals of advances in automotive medicine. Association for the Advancement of Automotive Medicine. Annual Scientific Conference, 2013 Kristy Arbogast, Caitlin Locey, Rachel Hammond, Aditya Belwadi