Attaining a sufficient level of safety from the point of view of stability is typically considered to be a matter of design。 However, it is impossible to ensure safety only by design measures, and operational measures can then represent a complementary tool for efficiently and cost-effectively increasing the overall safety of the vessel。 Time could therefore be coming for systematically considering operational measures as a recognised and regulated integral part of a holistic approach to ship safety from the point of view of stability。 This paper therefore aims at capturing recent trends of research targeting operational safety measures, with specific attention to the intact ship condition。 Open challenges and opportunities for research are identified, potential benefits and shortcomings of different options are discussed, and needs and possibilities for further developments in this area are explored。 As an overall goal, this paper aims at providing food for thoughts as well as a ground for further proceeding towards the target of implementing a virtuous integrated approach to intact ship safety, from the point of view of stability, which gives due credit to effective and robust operational risk control options。1。  Introduction 81989

Attaining a sufficient level of safety from the point of view of stability is typically considered to be a matter of design。 It is indeed often assumed that the required level of safety is to be guaranteed by implementing proper passive measures at the design stage, in the form of design characteristics (hull shape, subpision, systems redundancy, etc。) and in the form of limita-tions on the acceptable loading conditions。

The matter of safety-by-design, both in intact and damaged condition, has been, and of course still is on top of the agenda, especially regarding the rule-making process。 However, it is impossible to ensure safety only by design measures, and design rules implicitly assume a certain level of knowledge, skills, experience and prudence of ship masters and crew。 These human

factors, which are commonly referred to as “good/prudent sea-manship”, hence represent a crucial aspect in determining the ship level of safety。 The skills of existing officers are however chal-lenged by rapid development of unconventional ship types and shipping solutions。 In some dangerous, or potentially dangerous, operational situations, it can therefore be a great challenge for the ship officers to take the most appropriate decisions for reducing the risk level。 Such situations can be effectively addressed by operational measures aimed at providing a decision support for the crew (Bačkalov et al。, 2015; Bulian et al。, 2015; Ovegård et al。, 2012; Shigunov et al。, 2010, 2013; Song and Kim, 2011)。 The implementation of operational risk control options can represent a valid tool for efficiently and cost-effectively increasing the overall level of safety of the vessel, both in intact and in damaged con-dition, also in those cases for which design changes would not be cost-effective。 This is typically the case with issues associated with dangerous dynamic stability phenomena in intact condition。

In fact, looking at numerous accident reports it can be easily understood that several accidents could have been avoided, or at least mitigated, by implementing appropriate operational coun-termeasures。 Depending on the case, such operational risk control

Please cite this article as: Bačkalov, I。, et al。, Improvement of ship stability and safety in intact condition through operational measures: challenges and opportunities。 Ocean Eng。 (2016)

options could be aimed at the prevention of the occurrence of the accident (measures aimed at the reduction of accident frequency/ likelihood) or at the mitigation of its consequences。

Although operational measures become effective during the actual life at sea of the vessel, the combination of planning and implementation of such measures involves both the design and the operation phases of the vessel。 It is therefore needed to properly “design operational safety measures”, both for intact and for damaged condition。 Indeed, operational measures are expected to be of different nature and to follow different approaches when considering an intact condition (a “normal state” of the vessel) and a damaged condition (an “abnormal state” of the vessel)。