Evaluation of the extent of bodily injury under reproducible accident-conditions offers a means of testing auto-safety measures. However, although the weight and dimensions of accident-trial dummies correspond to those characteristics of humans, dummies deform elastically in crashes whereas humans generally react plastically, i.e. with broken bones and torn tissue; hence, direct evaluation of equivalent bodily injury is not possible. The paper presents methods for correlating measurable quantities in dummy-trials to equivalent injuries sustained by humans under similar circumstances.Limitations of the linear AIS scale of injury severity lead to formulation of hyperbolic tangent curves which directly relate mechanical loading to extent of injury (EIS: equivalent index of severity). The EIS formulation is then developed for evaluation of injury to particular body parts~head, chest, etc.~and is subsequently extended to a grading of total bodily injury.