Determination of collision criteria and causation factors appropriate to a model for estimating the probability of maritime accidents

Abstract

In this paper, a study leading towards a new definition of a ship–ship collision criterion, allowing further estimation of the probability of maritime accidents is conducted. The criterion is called the minimum distance to collision (MDTC) and reflects the shortest distance between two ships at which they must take evasive actions to avoid a collision. The new criterion is evaluated by means of a series of simulations using a ship motion model for a range of ship types, courses and speeds and thus its dynamic nature is recognised. It addresses the crossing type of ship–ship encounter. Additionally, this study defines a causation factor, which quantifies the proportions of cases in which two ships meeting each other end up having a collision. The causation factor is obtained in the course of maritime traffic analysis and accidents statistics. A comparative method is applied and the causation factors are determined for three different meeting types (head-on, crossing and overtaking). The causation factors obtained are valid for the MDTC model, chosen location and prevailing traffic conditions. The major factors affecting the MDTC criterion and relevant steps in the evaluation of the causation factors are described and discussed in the paper.