Toward a Method Evaluating Control Actions in STPA-Based Model of Ship-Ship Collision Avoidance Process

As system-theoretic methods of safety assessment are developed, certain aspects of them remain under-explored, including the question of prioritizing one control action's adequacy over another. This paper investigates this feature based on the analysis of a process of merchant vessels' collision avoidance. We first elicit experts' views on the structure of the process and importance of particular interactions occurring therein. Thence, we analyze a number of incident reports to examine the percentage of cases in which failure to ensure the particular control action contributed to the loss. By comparing the results, we strive to determine whether any of the approaches might be beneficial in determining safety control actions' priorities.