The Biomechanics Behind Child Passenger Safety

October 8, 2013

If you are a Research in Action reader in the field of child passenger safety, you know the safest ways to properly restrain a child in a motor vehicle and may even work to educate parents on this topic. What may be less obvious, however, is the complex body of biomechanical engineering research behind the current best practice recommendations.

As Project Manager for Pediatric Biomechanics research at CIRP, I don’t often have the opportunity to interact with child passenger safety practitioners who regularly work with families. So I was excited to present an overview of CIRP@CHOP’s engineering work in this field at the 2013 Maine Child Passenger Safety Conference, sponsored by the Maine Department of Highway Safety. I thought I’d share some highlights with our Research in Action audience.

Elements of a Car Crash that Inform Restraint Design
1. Crash dynamics (vehicle impacts object)
2. Occupant kinematics (occupant impacts vehicle interior)
3. Injury biomechanics (severity of injuries sustained by internal organs)
A comprehensive understanding of all three elements is essential for advancing child passenger safety.

If you were to ask your family, friends, or co-workers to define a car crash, their description would likely focus on the vehicle impacting another vehicle. However, in reality, car crashes involve much more. There are actually three distinct impacts that occur during a crash. [See box at right.] Age, in particular, has a strong influence on the second and third elements of a car crash. Although children may seem like “small adults,” in reality children’s bodies are vastly different from adults’ in terms of not only size, but also skeletal structure, cervical spine development and, perhaps most importantly, flexibility. Therefore, they must be restrained differently in motor vehicles so that the most vulnerable parts of their bodies (head, neck and thorax) are properly protected in the event of a crash. You can read more about how children are injured in crashes and CIRP@CHOP’s recommendations on developing more accurate child anthropomorphic test devices (ATDs), or crash test dummies, in our 2010 Child Passenger Safety Issue Report.

Biomechanics Applied In Sled Test

To further enhance our knowledge of how children’s bodies move in crashes, CIRP@CHOP researchers are using a custom-built crash sled to test crashes with child and adult volunteers in a collaborative effort with Rowan University in Glassboro, NJ. In this series of studies, we test pediatric volunteers in safe, low-speed impacts. Volunteers are restrained with regular seat belts and the crash sled simulates a head-on bumper car crash that you might experience at an amusement park.


A 6-year-old anthropomorphic test device (ATD) is restrained on the crash sled for testing. The white dots are the motion capture technology our researchers use to track movement during crash testing.
 

An amusement park bumper car used as a model for CIRP's low-speed, safe pediatric volunteer crash testing.

The data collected from motion analysis markers on the volunteers' bodies describe differences between reaction of child and adult bodies to crash forces. These biomechanics analyses ultimately inform design modification to vehicles and restraints aimed at reducing pediatric injury in motor vehicle crashes, a shared goal with CPS practitioners in the field.

I heard from emergency medical service (EMS) workers that the talk helped them to better understand injuries to look for in children in crashes and, from CPS technicians, that biomechanics can aid how they educate parents about proper restraint. The practical, real world questions and comments helped to expand my understanding of the impact research has on practitioners who work directly with families. I look forward to more opportunities for collaboration and open dialogue.