Consequences of ship collisions in Swedish waters: A Coastal State risk management perspective

Ship collisions remain a persistent safety concern in high-density and geographically constrained maritime regions such as the Baltic Sea. This study examines collision risk in Swedish waters using multiple sources, integrating accident data from Transportstyrelsen with the operational activity data that the Swedish National Road and Transport Research Institute VTI calculated based on HELCOM’s AIS-data and supplementary environmental and economic datasets. A total of 525 collision occurrences (2011–2023) were analysed, with a harmonised subset of 429 collisions subjected to exposure normalised assessment. Collision frequencies were normalised against three measures of activity which include distance sailed, operational time and number of unique ships to provide strong interpretation of risk beyond absolute accident counts. The results show that collision occurrence is primarily driven by operational exposure and navigational context, with passenger ships exhibiting the highest collision rates due to intensive operations in confined and high traffic density environments. Dry cargo ships display more stable and proportional risk patterns, while tanker collisions are characterised by low frequency but high variability, limiting trend-based interpretation. Scenario analysis identifies three dominant risk structures such as high-frequency, low-severity operational collisions, interaction driven collisions with higher severity potential and low-frequency, high consequence events, especially involving tankers. Although most collisions result in minor consequences, the study highlights that overall risk is shaped by rare but high-consequence events, especially in environmentally sensitive areas of Baltic Sea. The findings demonstrate the importance of integrating exposure, consequence severity and operational context in maritime risk assessment and support the refinement of risk-based safety management and policy development in Swedish waters.