Declarative ship arenas under favourable conditions

According to maritime regulations, a collision-avoidance action shall be taken at an “ample time” while strict interpretation of this term is ambiguous. Evasive manoeuvres, executed by marine navigators on a daily basis, are usually carried out well in advance, while the distance at which they decide to perform such a manoeuvre is mostly subjective and results, e.g., from the navigator's seagoing experience. A proper understanding of the decision-maker's behaviour under favourable conditions, when time pressure does not exist, seems to be essential for the future of maritime safety. This could enable the translation and quantification of seafarers' routine actions, taken many times a day, into collision-avoidance algorithms suitable for Decision Support Systems (DSS) or Maritime Autonomous Surface Ships (MASS). The literature lacks extensive research on this subject, as it focuses mainly on safety-critical actions, which are important but rare events. Therefore, this study aims to fill this gap by surveying practitioners and extracting their expert knowledge. Based on an online survey, the declarative ship arenas, reflecting the distance of evasive manoeuvre initiation, were determined and analysed. The findings revealed that, depending on the participants' profiles, a range of responses among the groups reaches up to 2 NM. The results indicated that navigators become less consistent with growing experience. Determined declarative arenas were consequently incorporated into a simulation-based case study of a passenger ship. The conducted simulations indicated that for several scenarios, the passing distances resulting from the execution of an evasive manoeuvre as per declarative arena were less than 0.5 NM, potentially leading to dangerous situations at close range. This results most likely from an overall problem of translating the distance of manoeuvre initiation into the final passing distance. The findings of this research may be found interesting by shipping companies preparing bridge procedures or for scholars and industry representatives preparing intelligent collision-avoidance solutions for maritime transportation. • The survey assessed preferred evasive manoeuvre distances per COLREGs' “ ample time” . • Ship arenas depicting respondents' sea experience and area type are introduced. • Collision avoidance preferences were investigated via computer simulations. • Some of the declared manoeuvre distances may be considered practically unsafe.