Int. J. Decision Support Systems, Vol. 2, Nos. 1/2/3, 2016 109 Copyright © 2016 Inderscience Enterprises Ltd. Risk assessment of ship-to-ship transfer operations based on stochastic criteria evaluation and intervally scaled importance weights Dimitrios I. Stavrou* and Nikolaos P. Ventikos National Technical University of Athens, 9 Iroon Polytechniou str., Zografou 15773, Greece Email: dstavrou@central.ntua.gr Email: dstaurou@gmail.com Email: niven@deslab.ntua.gr *Corresponding author Yannis Siskos University of Piraeus, 80 Karaoli and Dimitriou str, Piraeus, 185 34, Greece Email: ysiskos@mailhost.unipi.gr Abstract: Ship-to-ship (STS) transfer of cargo operations suffers inherently from risks that can compromise the success of such operations, leading to an accident with adverse effects on human lives and the environment. A feasible way to tackle the risks of STS transfers is through the use of multicriteria decision aid (MCDA) methodologies. This paper aims to develop an MCDA model to evaluate risks of an STS transfer based on the outranking relation concept. The proposed methodology uses confidence indices to compare alternative risk scenarios on stochastic risk criteria evaluation. To do so, a team of experts evaluate the scenarios regarding three risk factors; the likelihood of a scenario to occur, the severity of the scenario and the ability to detect the risk on time. Next, fuzzy domination relation is applied to complete the ranking of the risks. Finally, robustness analysis is performed to control the model’s stability. Keywords: maritime activities; risk assessment; uncertainty; multicriteria analysis; ship-to-ship transfer. Reference to this paper should be made as follows: Stavrou, D.I., Ventikos, N.P. and Siskos, Y. (2016) ‘Risk assessment of ship-to-ship transfer operations based on stochastic criteria evaluation and intervally scaled importance weights’, Int. J. Decision Support Systems, Vol. 2, Nos. 1/2/3, pp.109–134. Biographical notes: Dimitrios I. Stavrou serves in the Hellenic Navy as a Lieut. Commander Officer. He is also a Naval Architecture and Marine Engineer by the NTUA, Greece. He is currently a PhD candidate at the NTUA. His research focuses on safety and risk analysis/assessment of maritime activities, human factor, multi-criteria analysis and decision support systems. He is studying STS transfer of cargo operations and associated issues. In 2012, he received the ABS Scholarship Award for distinguished studies. He currently participates to the ‘IKY fellowships of excellence for postgraduate studies in Greece-Siemens program’.