Characterizing Child Head Motions Relative to Vehicle Rear Seat Compartment in Motor Vehicle Crashes

Improved padding or other countermeasures in vehicle rear compartments could reduce the incidence of head trauma for child occupants. However, knowledge of likely child head impact locations for a range of crash scenarios is needed to determine which areas and structures should be padded and where a side curtain should be deployed to protect child occupants. The objective of this study is to use a scalable MAthematical DYnamic MOdels (MADYMO) model of a child occupant to estimate the distributions of possible head impact locations as a function of crash type, vehicle interior characteristics, and child size. To achieve this goal, a series of simulations using a scalable MADYMO child anthropometric test device (ATD) model was conducted. The geometries of the second-row compartment from 5 vehicles were recorded using a laser scanner to provide high-resolution data for assessing probable head contact zones. Distributions of lateral and longitudinal delta V were calculated as a function of principal direction of force (PDOF) using the National Automotive Sampling System – Crashworthiness Data System (NASS-CDS) dataset to provide proper simulation conditions based on real-world crashes. Simulations of crashes ranging from pure frontal to pure side impact (9 o’clock to 3 o’clock) with child ATDs with and without backless boosters were conducted using University of Michigan Transportation Research Institute's (UMTRI’s) parametric child ATD model in MADYMO, UMTRI's child ATD positioning procedure, and UMTRI's automated belt-fit and crash simulation system. The simulation results were used to create a model of the spatial distribution of head trajectories based on child body size and crash direction. By combining the head motion model and the vehicle second-row geometry models, the likely head contact zones with respect to interior components were identified. The findings of this study provide a reference for future vehicle rear compartment design to reduce head injuries for older children.