Dynamic Comparison of Large Omni-directional Child ATD to Pediatric Volunteers

Principal Investigator: Tom Seacrist, MS, 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 comparison of volunteer-ATD response in low-speed oblique impacts, featuring left to right: an 11-year-old human volunteer, the LODC, the Q10, and the HIII 10.

Research has shown that the head is the most commonly injured body region among children in motor vehicle crashes. To better mitigate these injuries, pediatric anthropomorphic test devices (ATDs), or crash test dummies, must mimic pediatric motion and internal forces as well as accurately predict injury potential during a crash. Previous studies of pediatric ATDs have shown an overestimation of upper neck loads and injury risk due to limited biofidelity of the ATDs. Recently, a large omni-directional child (LODC) ATD has been developed in an effort to improve biofidelity through a more realistic shoulder construction, softer cervicothoracic junction, and a multi-segmented, more flexible thoracic spine compared to the Hybrid III 10-year-old dummy. This study sought to evaluate the influence of these modifications on LODC neck loading by comparing its response to previously collected child volunteer data in low-speed sled tests. 

Low-speed (<4g) sled tests were conducted with the LODC, which was restrained using a 3-point seat belt. Photo-reflective targets were placed on important anatomic landmarks, such as head top, and were captured using a 3D near infrared tracking system. Variables considered were shear force (Fx), axial force (Fz), and bending moment (My) about the upper neck. These parameters were calculated using standard equations of motion. These data were then compared to previous data from 9- to 11-year-old pediatric volunteers, the Hybrid III 10, and the Q10 that were tested utilizing similar methods. 

The LODC significantly underestimated mean shear force compared to the HIII 10, Q10 and volunteers. The LODC also underestimated axial force compared to the volunteers, yet was closer to volunteer levels than both the HIII 10 and Q10. These differences are likely due to the LODC’s greater flexibility, especially in the thoracic region of the spine. A shift in force distribution from shear to axial was displayed, likely due to greater head rotation displayed by the LODC than the HIII 10 or Q10 ATDs. 

The LODC has the potential to address one of the primary biofidelity issues with the current pediatric ATDs – the rigid thoracic spine.  As continuous improvements are made to ATDs, future work should continue to investigate the acceleration and loading of pediatric ATDs in comparison to human volunteers; these data provide valuable information on the biofidelity of the recently developed LODC that have led to newer iterations. 

Project Team Member

Caitlin Locey, BS, Children’s Hospital of Philadelphia 


Gretchen Baker, University of Kansas 

IAB Mentors

Jason Stammen, National Highway Traffic Safety Administration