Novel Safety Index Calculation Models for Ship Collision Risk Assessment to Enable Sustainable Maritime Transportation

Maritime safety is a key element of sustainable maritime transportation, particularly in strait regions with dense vessel traffic and dynamic environmental conditions that increase collision risk. Based on historical records, ship collisions can result in severe human casualties, environmental pollution, cargo and infrastructure damage, operational disruptions, and substantial economic losses; therefore, a reliable and integrated safety assessment is essential to support safe, efficient, and sustainable maritime transportation. This study proposes a novel safety index framework to assess the ship’s collision risk by integrating vessel characteristics, ship encounter conditions, operational time parameters, and oceanographic factors such as currents and waves. The analysis is based on questionnaire data, AIS records, and oceanographic information collected over a one-month period with a three-minute temporal resolution. Case studies are conducted in the Bali Strait and the Lombok Strait using grid-based spatial segmentation to represent spatial risk patterns. Two safety index models are developed. Model I emphasizes vessel, encounter, and temporal factors, while Model II extends the assessment by fully integrating oceanographic conditions. To improve interpretability and practical applicability, the calculated safety index is further transformed into a normalized safety index with values bounded between 0 and 1, allowing for explicit risk classification. A multivariate contribution analysis is applied to identify dominant risk factors. The results show that the maritime risk in both straits is mainly influenced by vessel traffic intensity, sailing hours, days of the week, and environmental conditions. High-risk zones in the Bali Strait are concentrated near Ketapang and Gilimanuk Ports, while elevated risks in the Lombok Strait are observed near Padangbai and Lembar Ports and along the ALKI II shipping route.