All injuries require an expenditure of energy. Here it is postulated that injury severity is proportional to Peak Virtual Power (PVP). PVP is compared to AIS scores for frontal impact with belted drivers, for all types of injuries and all body regions, from the Co-operative Crash Injury Study (CCIS) and NASSCDS databases. The excellent correlations obtained show that the AIS score is linearly proportional to Peak Virtual Power, which is proportional to DV3 for restrained occupants, and DV2 for unrestrained occupants. Therefore, although phenomenological, AIS appears to measure a physical quantity. It is concluded that there appears to be a “Master Curve” of AIS versus mean DV for car occupants, implying that the amount of power for a given injury level is a constant, irrespective of injury type. There appear to be significant differences between the AIS scores for abdominal injuries between CCIS and NASS-CDS, and detailed case studies should be conducted to resolve the differences.