A novel index for real-time ship collision risk assessment based on velocity obstacle considering dimension data from AIS

Abstract

An index for real-time collision risk assessment is the basis for the safe navigation of ships. To consider dimension related factors more accurately and objectively in the collision risk index, and to enhance the readability of the index in collision avoidance decision-making, we propose a novel index by combining the dimension data from automatic identification system (AIS) and velocity obstacle approach, namely the ‘margin of projected collision (MPC)’ index. Compared with traditional existing indicators, our proposed index can more accurately and objectively judge whether the two ships collide if the current state of motion is maintained. Also, the numerical meaning of quantified risk is innovatively directional in the state of motion (i.e., course and speed), so the proposed index may additionally provide navigation assistance information including proactive warnings for dangerous behaviour and behaviour references for collision avoidance. In addition, through the real encounter cases with high collision risk, we demonstrate that our proposed index has high practical value and can be used as a good supplement to the traditional collision risk index, especially in high-precision applications such as waters with heavy maritime traffic and maritime autonomous surface ships (MASSs).