Seventeen left lateral impact experiments were performed using anesthetized swine to determine the biomechanics of injury production in this impact mode. Two series of eight animals were used and one animal served as a control. In the first series of experiments, rigid thoracic and pelvic loading surfaces were separated by an “interplate gap” of 20.3 cm (8”). In the second series of experiments, the interplate gap was filled by a rigid plate mounted flush with the thoracic and pelvic loading surfaces. Impact velocities ranged from 7.2 to 15.0 m/s (about 15 to 30 mph).Injury patterns for the liver, spleen, and rib cage were significantly different in the two series of experiments (level of significance > 90%). The causative factor responsible for the different injury outcomes was the interplate gap.The conclusion of this report is that loading-surface discontinuities can cause significant injury. Therefore, in design of side doors and interiors, consideration should be given to the location of surface indentations (such as map pockets) as well as surface protuberances (such as armrests).