Trigger event(s) identification for switching operational mode of Maritime Autonomous Surface Ships

Maritime Autonomous Surface Ships (MASS) are expected to operate in various operational modes (OMs). To support the decision-making on OM switching, navigational risk in three OMs, i.e., manual control (MC), remote control (RC), and autonomous control (AC) had been discussed in our previous studies, while the time for switching is still an open question. Based on our previous studies, this paper proposed a 4-step framework, including the development of Accident Scenario (AS), operational risk comparison, the establishment of Sub-AS, and trigger event(s) determination. In the case study, the scenario is derived from a ship-bank allision accidents, where the 3rd DoA MASS is employed; the inputs of failure modes (FMs) are evaluated in three OMs by interviewees; the results reveal that the MC is the optimal OM to switch to, and when deviation in course occurred, such switching should be performed. Additionally, we found increasing the number of interviewees could reduce the uncertainty and enhance the reliability of results.