A New Collision Risk Assessment Algorithm Based on Ship’s Finite-Time Reachable Set

Collision risk assessment is essential for navigators or automatic navigation systems to identify potential risks in specific encounter scenarios and to make informed decisions regarding subsequent collision avoidance measures. This paper proposes a quantitative ship collision risk assessment algorithm based on the reachability of the vessels. The concept of a ship’s finite-time reachable set is introduced to characterize spatial area accessible to the vessel within the navigator’s “action time”. A novel risk assessment algorithm is proposed that takes into account not only the probability of collision but also the anticipated consequences. Compared to previous risk assessment methodologies, this new quantitative assessment algorithm can provide both upper and lower bounds of ongoing collision risk according to the real-time motion characteristics of ships. The effectiveness of the new risk assessment algorithm is examined by simulation studies that cover three typical encounter situations: head-on, crossing, and overtaking. The results show that our risk assessment algorithm can accurately predict the trend of risk variation.