1. Introduction
The present paper reviews published research on procedures for reducing the high economic, environmental and human costs associated with ship collisions and grounding and outlines a probabilistic procedure by which the maritime industry can develop performance based rules to reduce the risk associated with collision and grounding events. The paper describes mathematically based procedures for identifying economic risk control options related to prevention and mitigation of damages due to collision and grounding events. Wang et al. [1] published in 2002 a review article in Marine Structures on the assessment of a ship’s performance in accidents. Therefore, the main focus of the present paper is on more recently published research results.
The initial part of the paper reviews published research on acceptance criteria for costs associated with collision and grounding events. A first step for a rational reduction of risk related to hazards, such as collision and grounding, must be to establish a comprehensive risk evaluation criterion for ship design and for operations. Without a proper, generally agreed on evaluation criterion it is not possible to find the balance between safety in terms of risk reduction and the cost to the stakeholders.
Any risk evaluation criterion must include the probability of the considered hazard. Therefore, the second part of the paper is devoted to tools for determining the ship and route specific probability that collision, contact or grounding events will take place.
The probability of the occurrence of collision, Fig. 1, and grounding events may be computed from historical data, expert opinions and predictive calculations. Historical data provides realistic figures which are, nevertheless, difficult to use for future predictions since they are relevant to ship’s structures which may differ from those used today, and they do not take into account the development in operational procedures and new navigational equipment. For these reasons, mathematical models for prediction of the frequency of hazard occurrence are an important first step for a rational risk assessment procedure. Such probabilistic analyses must involve identification of a number of different collisions and grounding scenarios, each associated with a probability level. The impact on the ship is then calculated as the sum of the products of the consequences related to each of these collision or grounding scenarios and the probability of their occurrence. It is a well known fact that usually the most cost-effective way to reduce risk is by reducing the probability that adverse events take place, see [2]. A number of frequency prediction models have been developed in recent years, which together with external energy analyses can be used to determine probabilistic distributions of energy released for crushing of structures.