Novel Safety Index Calculation Models of Ship-Ship Collision Risk Assessment

Maritime safety is a crucial aspect in busy and complex shipping lanes, particularly in strait areas that are prone to accidents due to high vessel traffic and dynamic envi-ronmental conditions. This study aims to calculate a maritime safety index by consid-ering various factors, including vessel characteristics, ship encounter conditions, oper-ational time parameters, and oceanographic conditions such as currents and waves. The data used consist of questionnaires, AIS data, and oceanographic information, collected over a one-month period at three-hour intervals. The case study focuses on the Bali Strait and the Lombok Strait, with spatial segmentation into grid cells to sup-port spatial analysis. The safety index is calculated using two models: Model I com-bines vessel and encounter characteristics with temporal parameters, while Model II incorporates oceanographic factors into the assessment. Following the index calcula-tion, multivariate analysis conducted to identify the key factors that significantly in-fluence maritime safety levels. The results show that navigation risks in both straits are mainly influenced by vessel traffic, sailing hours, days of the week, and environmental conditions. In the Bali Strait, the highest risks occur near Ketapang and Gilimanuk Ports, while in the Lombok Strait, Padangbai, Lembar, and the ALKI II route show ele-vated risks. Multivariate analysis reveals that longer vessels, higher speeds, and dy-namic sea conditions dominate in Lombok, whereas older vessels and closer spacing are more critical in Bali.