Considerable advances in wheelchair occupant frontal impact safety have been achieved, but further research in rear impact is required. Future analysis would benefit from more biofidelic representation of wheelchair occupants, including effects of postural deformities such as scoliosis. In this work, the development and validation of a Madymo baseline wheelchair and occupant model for rear impact analysis is presented. In the model, the BioRID rear impact dummy is seated in a rigid wheelchair without a headrest and subjected to a lOg rear impact pulse. Sled tests of this configuration were performed and used to provide validation data for the numerical model. A comparison of the kinematic model predictions with the high-speed video test data showed a good ability to reproduce the whiplash motion sequence. Furthermore, the model correlates with the experimental time histories with an average difference of 10%. The model is therefore considered a valid representation of a 50th percentile male occupant of a rigid wheelchair in rear impact.

This model was then adapted by implementing scoliosis and the influence of this w’as evaluated by comparison with the baseline model and based on this work there were the two major findings. Firstly it was found that the altered shape of the scoliotic spine introduces a point loading effect on the occupant. Secondly there is an associated stiffness introduced by the deformed shape of the spine. Both of theses factors lead to increased loading on the thoracic spine with the the largest increase in loading being on the apex of the scoliotic curve. The initial position of the occupant in the wheelchair was also found to have a significant effect on occupant loading, with initial proximity to the wheelchair reducing the loading. This has implications for seating clinics which adapt wheelchairs to suit the needs of the occupant. The wheelchair of the model w^as altered to represent these adaptations. It was found that the addition of postural supports can reduce the loading on the occupant as they mimic the close initial contact between occupant and the wheelchair. However the stiffness of the surfaces of such supports was also found to have a significant effect with softer foam surfaces bottoming out under crash loading which increases the forces on the occupant.

This work presents the first evaluation of wheelchair occupant loading in a rear impact on the whole spine. It also supports the hypothesis that alterations to the standard representative occupant and wheelchair models alter the loading on the spine in a rear impact.