A COLREG-compliant ship collision alert system for stand-on vessels

Bridge alarms are a plausible way to reduce the ship collision probability by timely alerting the officer on watch of a conflict. However, there currently are no dedicated methods for alerting a stand-on ship to compensate the unawareness of or inactive response of a give-way ship to dangerous encounter situations. Therefore, this article proposes a collision alert system from the stand-on ship perspective to trigger the stand-on ship's involvement in the conflict elimination. The developed method quantifies the terms of the COLREGs regarding the stand-on ship's responsibility for conflict elimination. The conflict severity is divided into 9 classes based on the ship intention estimation, conflict evolution analysis and COLREGs scrutiny. These are linked with the 4 stages of the encounter process to helps stand-on ship clarify her action responsibilities as per the rules and classify the alert into four levels. The available maneuvering margin of the stand-on ship is considered to improve the accuracy of severity ranking. The results of several case studies in open water with good visibility indicate that the proposed method can support the stand-on ship to correctly understand the rules and to fulfil her duties.