It was found that a combination of simultaneous and sequential variables, non of which is by itself sufficient, it responsible for causing accidents. Each accident may be classified by a single crucial event. The factors contributing to it may be described in terms of the points at which operations requiring state highway travel fail and the conditions of components of the road-driver-car system, that induce the failure. Operations may fail at any of three levels (evasive action, strategy, and trip planning), each of which has three phases - recognition of the situation, decision as to the required maneuver, and performance of the maneuver. Conditions which induce failure are of two kinds - attributes of the elements of the system (the trafficway, person making the trip, and the vehicle) and permanent and temporary modifiers which change attributes of the elements of the system. An interpretation of some of the more common descriptions of accident factors is used in the analysis of an actual accident. Abstracts of reference documents used in this report appear in the appendix.
Abstract