A combined program of accident investigation, staged collisions, and simulated collisions involving three-point harnessed occupants in frontal force collisions has provided a means of correlating injury with forces and/or other physical parameters associated with the injuries. With a strict screening to ensure complete data on each accident, 128 cases involving 169 occupants at barrier equivalent velocities from 2-53 mph were compared with the results from 11 staged collisions and 72 simulated collisions.There were 14 rib cage injuries ranging from single sternum fracture to seven rib fractures at velocities of 10-53 mph at injury levels of AIS 2 and 3. A single AIS 4 injury was the most serious injury and consisted of a ruptured spleen. The most serious brain injury was an AIS 2. Two cervical vertebra fractures were found, one of which was a 12-year-old male and the other a 76-year-old female. Only 14 occupants had AIS 3 injuries.No abdominal (except the ruptured spleen) organ injuries, thoracic organ injuries, breast injuries, clavicle fracture, or eye injuries were reported, and there were no AIS 5 or fatalities in the sample.It is concluded that: the harness is highly efficient in mitigating injuries, rib and sternum fractures are the more prevalent injuries, submarining is not a major problem, females are injured at lower collision severity than males, and age is an important factor in injury susceptability.The overall tolerance level for 50% injury at the AIS 3 level is 45 mph at an upper shoulder harness load of 1930 lb, a chest Gadd Severity Index of 560, and a peak resultant chest acceleration of 85 g.