Dynamics collision risk evaluation and early alert in busy waters: A spatial-temporal coupling approach

Ship collision is a significant threat to waterborne transportation safety in busy waters. In order to mitigate the probability of ship collisions, improve navigation safety, and reduce economic losses, this paper proposes a spatial-temporal coupling approach to ship collision risk evaluation for alert in busy waters. First, the probabilistic ship domain considering ship characteristics (e.g., ship length and ship type) is determined based on historical Automatic Identification System (AIS) data. Secondly, the calculation models of the spatial-temporal collision risk of two-ship and multi-ship scenarios are proposed by the overlap of probabilistic ship domains, ship approaching trends, and catastrophe theory. Then, the ship probability domain overlap and the time required for ship collision avoidance are considered to estimate the threshold value of spatial-temporal collision risk between two ships. Meanwhile, a multi-level alert method for ship collision is proposed according to the degree of intrusion into the ship domain, the spatial-temporal collision risk, and the threshold value of the spatial-temporal risk collision. Finally, an example analysis was carried out based on the AIS data of the Luotou Channel in Zhoushan, China. The results indicate that the proposed method can effectively characterize the collision risk when two-ship or multi-ship encounters in busy waters, and can accurately classify the collision alert levels. Compared with traditional existing indicators, it is concluded that (1) the proposed method, which integrates both spatial and temporal collision risk, effectively categorizes collision alert levels, (2) it overcomes the limitations of traditional collision risk assessment methods, particularly in reflecting nonlinear changes in collision risk, and (3) it can assess collision risk in busy waters.