Collision Rate as a Danger Criterion for Marine Traffic

Abstract

For many practical purposes it is desirable to have a yard-stick with which safety can be measured. A criterion for the estimation of the safety of ships against collisions is outlined in this paper. The method is based on mathematical simulation and embodies all relevant factors. Numerical results are given for the English Channel and the German Bight showing the effect of parameter variations.i. I N T R O D U C T I O N . A considerable change in the size and structure of marine traffic has taken place in the last two decades. This is mainly due to the jerky rise of cargo transport across the sea and new technical developments in the recent past. The number of tankers, for example, has doubled from i960 to 1980 and their tonnage has increased sevenfold. New ship types have come into the world such as fast container ships and medium-speed vessels for the carriage of dangerous cargoes such as gas and chemical tankers. In addition, numerous structures for oil and gas production have been erected at sea which only serve to complicate marine traffic flow.Contrary to some pessimistic forecasts the transport of goods by sea will be increasing in the future and so will the number of ships at sea. The reason is that there is no other means of transport which can carry so many goods as economically as a ship.With the growth of traffic density it has been assumed that the dangers of an accident would also increase. Bearing in mind the possible consequences of a ship casualty for human life and the environment, competent authorities have, therefore, taken steps to prevent accidents. (The types of accidents considered are primarily collisions and strandings.) Measures such as separating traffic, establishing radar chains and other navigation aids, monitoring and regulating traffic, etc. were introduced. Most of these measures, however, were taken without exactly knowing what degree of safety existed before and what degree is expected after the implementation of the measure. (Clearly absolute safety is unattainable in marine traffic.) In view of the high costs associated with the measures both for the administrative authority and the user, it seems desirable to know by what amount the safety is increased.A suitable means for quantifying the safety of marine traffic seems to be the accident rate. Because of the very complex nature of marine traffic, experience and historical data alone are not sufficient to identify safety. Modern techniques for the prospective assessment of safety such as Systems Engineering, in which all relevant factors appearing in the real situation are detected and considered, 82O3 NAV 39