Thoracic trauma is the principle causative factor in approximately 30% of vehicular collision deaths and is a contributive factor in approximately 70%. This impact trauma may be the result of loading from interior components of the vehicle or the result of loading from the restraint system. Restraint loading may be concentrated, such as loading from a seat belt, or distributed, such as loading from an airbag. This dissertation develops a set of tools for the prediction of thoracic injury potential, as defined by rib fractures, from restraint loading in a frontal impact. Sled tests using human cadavers and anthropomorphic dummies are used to evaluate the efficacy of proposed thoracic injury criteria, including chest acceleration, the viscous criterion, chest compression, chest compression velocity, and the combined thoracic injury criterion CTI. Rib fractures are shown to be a deformation-dependent injury and the maximum chest compression is shown to be an effective criterion for predicting rib fracture risk for a set of impact, restraint, and occupant characteristics. Further, the level of chest compression at which fractures initiate under frontal impact restraint loading, while dependent on the age and other characteristics of the subject, is shown to be approximately 25%--a value that is not sensitive to the particular restraint loading condition that generated the compression. A quasilinear viscoelastic characterization of the human thorax, which defines the compression response to belt-like loading, airbag-like loading, and steering wheel hub-like loading, is presented as a design tool as well as a tool for assessing the biofidelity of dummies. The force-deflection response of the thorax is shown to depend strongly on the anatomical structures that are engaged during loading, with the area of load distribution being a secondary factor.