A method for estimating propulsion risk of the ship casualty

Loss of the propulsion function by a ship is one of the most serious categories of hazardous events in sea transport. In specific external conditions it may lead to a loss of ship and environmental pollution. The consequences of propulsion loss by a ship are events classified by the International Maritime Organization as casualties or incidents. The probabilities of occurrence of the former events in a specific time unit constitute the propulsion risk of a ship. Determination of these probabilities is in practice confronted with difficulties connected with shortage of data. A method for estimating the risk caused by loss of a seagoing ship propulsion function is proposed. The estimation is fully based on the expert judgments. Expert is assumed to be well acquainted with the subject he is expected to formulate his judgment on. Expert should also be capable of formulating his judgment. This is connected with level of his education and the language used in the elicitation process, particularly as regards the parameters the expert is expected to estimate. This may be the language of numerical or linguistic values. Numerical values are better but are more difficult to articulate - also errors in judgments are more likely. To overcome this problem and to obtain a more accurate estimation, this study suggests using an analytic hierarchy process (AHP), which quantifies the subjective judgments and confirms the consistency of collected data. An example of the propulsion risk estimation of container carriers operating on the North Atlantic line allows to assess effectiveness of the method.