Understanding Reclined Small Occupants’ Kinematics in Frontal Crashes by Testing the LODC

Principal Investigator: Valentina Graci, PhD, Children's Hospital of Philadelphia


This project aimed to characterize the kinematics and kinetics of reclined child occupants with and without booster seats in frontal crashes by using the LODC ATD that was recently developed by NHTSA. We chose the LODC for this study because of its adjustability and flexible spine, which is ideal for examining reclined postures in vehicles.  


The LODC was tested in 12 simulated full frontal vehicle crashes, with and without low back booster seats, at the Medical College of Wisconsin. Three reclined seatback angles were compared: nominal (25º), moderate (45º), and severe (60º). We also examined scenarios with and without a pre-pretensioner seat belt. 3D motion capture and sensor data, including accelerometers, angular rate sensors, and load cells were used to measure the LODC response.


The booster seat prevented submarining (when the child slides under the seat belt) in all reclined seatback angles. However, we found that the compressive forces on the lumbar spine increased with the increase in recline angle and the presence of the booster seat. However, we don’t know if those forces can cause injury because our field does not have an injury risk curve for the pediatric lumbar spine to place these values in context.


These results lead to future research questions focused on modification of the vehicle seat pan to mitigate these forces. It would be great to extend this research to also examine the ATD response with reclined seatbacks when restrained in a high back booster, as well as other crash directions. 

Booster Seat Image
Test images at peak forward head displacement for the 45° (moderate) reclined condition with the booster seat (left) and without the booster seat (right).


Hans Werner Hauschild, MS, Medical College of Wisconsin; John Humm, PhD, Medical College of Wisconsin; Jalaj Maheshwari, MSE, Children’s Hospital of Philadelphia

IAB Mentors

Allison Schmidt, Britax Child Safety Inc.; Michael Kulig, Calspan Corporation; Suzanne Johansson, General Motors Holdings LLC; Susan Mostofizadeh, American Honda Motor Co., Inc.; Jerry Wang, Humanetics Innovative Solutions Inc.; Mladen Humer, Lear Corporation; Jason Stammen, National Highway Traffic Safety Administration; Schuyler St. Lawrence, Toyota USA; Uwe Meissner, Technical Advisor