INLAND WATERWAY TRANSPORT - MODELING THE PROBABILITY OF ACCIDENTS

In 1989 the Dutch government started the project ''Safety in Inland Wa terway Transport'' to establish a minimum safety lever and to develop a model to assess the effect and effectiveness of new safety measures. This model is called the Risk Effect Model, and calculates the integr al impacts of safety measures for the entire waterway system including the risks of transporting dangerous goods. The final result of the pr oject is a framework for evaluation, which supports cost-benefit analy sis by weighing negative economical effects against achievements in sa fety, for different measures. In this paper we will present the method s which have been used to calculate the probability of an accident, us ing casuistry. In this project the probability of an accident is model led per elementary traffic situation (a combination of several ships c arrying out a ship motion produces a traffic situation), The number of accidents can be estimated by the number of elementary traffic situat ions multiplied by the probability of an accident per elementary traff ic situation. In the paper we describe fitting procedures in order to obtain the model that ''forecasts'' the probability of accidents as fu nction of waterway attributes and circumstances. We have used Generali zed Linear Models (GLM), which do not need the assumption that the acc ident probability is normally distributed. We have used the binomial a pproach in the GLM models. We present the results of the fitting proce dures for one group of elementary traffic situations (through-going tr affic mutually). The primary governing variables appear to be visibili ty, wind speed, the ratio of the navigable width and the necessary wid th for an elementary traffic situation, and the bend radius of the wat erway. The circumstances (visibility and wind speed) are more explanat ory with respect to the probability of accidents than the waterway cha racteristics are.