ABSTRACT
In recent years, ship-to-ship collision risk assessment in individual sea areas have attracted increasing interest to support the development of traffic safety measures, assist ship operations and enhance vessel traffic management. To address this, the authors have proposed several methods for assessing collision risk distributions, including a novel approach that subdivides large sea area into numerous smaller regions and estimate collision risk in each subregion. Although the applied formula aligns with conventional methods used for large sea areas, the extent to which local risk characteristics are considered when applied to smaller regions remains largely untested. Dividing regions into subregions poses challenges due to the limited availability of accident data to validate the estimation results. In this study, the concept of near collision was first adopted to supplement the collision data, and its characteristics were investigated. Then, the results of encounter assessment in small regions using the encounter frequency (EF) method and the obstacle zone by target (OZT) method are compared with near collisions to examine whether the characteristics of the hazards identified from collisions and near collisions are reflected in these results.
