This paper analyzed the mechanisms of injury in high speed, right-lateral impacts of stock car auto racing, and interaction of the occupant and the seat system for the purpose of reducing the risk of injury, primarily rib fractures. Many safety improvements have been made to stock car racing recently, including the Head and Neck Support devices (HANS®), the 6-point restraint harnesses, and the implementation of the SAFER Barrier. These improvements have contributed greatly to mitigating injury during the race crash event. However, there is still potential to improve the seat structure and the understanding of the interaction between the driver and the seat in the continuation of making racing safety improvements. This is particularly true in the case of right-lateral impacts where the primary interaction is between the seat supports and the driver and where the chest is the primary region of injury. Currently, the driver kinematics and the interactions between the driver and the seat/restraint system at such high speeds are not clearly understood, due to the limitations of physical testing. Therefore, for this study the Total HUman Model for Safety (THUMS) FE model was combined with a detailed NASCAR® cockpit and typical racing seat structure, in order to simulate the driver in a right-lateral high acceleration impact. Simulations were conducted with two varied accelerations (25G and 70G), to judge the effect on injury risk. Additionally, finite element (FE) simulations were run to investigate the risk of injury by varying chest support length, rigidity, and shoulder support vertical angles, representing the variability found in real-world racing seat structures. For all of these simulations the distributed forces to the driver were analyzed and compared to injury tolerance limits found in literature. Additionally, strain analysis of the cortical bone was used to estimate bone fracture risk. By comparing all of the analysis results the most effective structure found to help reduce the possibility of rib fractures was that of a full rigid chest support structure (covering the length of the lateral ribs) with Energy Absorbing (EA) foam padding. This allowed for optimum distribution of force across the lateral chest which prevented force concentration to local areas of the ribs. It also provided a reduction in the applied shoulder force, hence, reducing the load to the clavicle. This study successfully simulated high speed right lateral impacts using the human finite element model, THUMS, and demonstrated mechanisms of injury for rib fractures which can be improved upon through seat structure modifications to help reduce the risk of injury in such crashes.