What happens, and why, in road accidents

Abstract

This paper suggests how to describe what happens in a road accident, and why. But road accidents as a whole are too varied, and some smaller concept is needed. The strategy here is to select some class of accidents that are similar, split the events of that class of accident into stages, and attempt to understand the stages. (a) The example selected is the class of accident in which a car being driven forwards normally is suddenly faced with an obstacle in front of it. (b) Such accidents are split into three stages. 1, Preceding appearance of the obstacle. 2, From appearance of the obstacle to when the car strikes it (or stops). 3, After first contact is made (but this is not discussed in this paper, as it is reasonably well-understood in principle). (c) For stage 2, a model is proposed that implies an elementary equation for impact speed. The equation involves five quantities, namely, travelling speed, range of sensor, distance of object, reaction time, and braking strength. (d) For stage 1, cause of accident is approached using two questions. Why was the obstacle present? And, if it was present deliberately and because of human error, what was the error? Suggestions are made for classifying the answers. (e) In many of the road accidents with two active participants, one has generated the danger and the other has reacted. If data analysis proceeds without their being disaggregated, it may become difficult to perceive factors and patterns of factors that are relevant to crash causation and outcome. This disaggregation may be particularly useful when one participant is a pedal cyclist.