Abstract
An analysis is made of human physical and psychological characteristics and the effect of these upon the driver-vehicle-highway-environment situation. In order to display this complex situation effectively, a conceptual model is presented. The model is based upon basic theories of psychology, physiology, information processing and servomechanisms. The degrading effect of a variety of pathological states on man's performance is also analyzed. Limitations added by the other factors in the system are considered and several criteria for safe control and tranportation are included.