Abstract
Transportation (un)safety is the result of a complex process in the transportation system. A large number of variables (characteristics of the system elements) with many interactions, produce a complex network of relationships expressed in "system behaviour". In this network of relationships, man as an element in the transportation system has the greatest number of degrees of freedom. His behaviour is therefore the most difficult of all to predict. Theories on the overall process in the transportation system are therefore dangerous and misleading. Theories only have predictive force if all relevant subprocesses are distinguished