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The growing implementation of Decision Support Systems on modern ships, digital-twin technology, and the introduction of autonomous vessels cause the marine industry to seek accurate modeling of vessel response. Despite the contemporary 6DOF models can be used to predict ship motions in irregular waves, the impact of their stochastic realization is usually neglected and remains under-investigated. Especially in the case of turning, differences arising from the stochastic representation of the waves may result in excessive ship motions or even stability failure during maneuver execution. Therefore, in this study, statistical distributions of maximum amplitudes of roll, pitch, and lateral acceleration calculated in two representative locations on board a passenger vessel were analyzed concerning stochastic wave realization and existing extremes. The research utilized 6DOF simulation data and numerous realizations of the irregular wave with random phases of its components. Furthermore, the required number of wave realizations allowing for capturing the actual ranges of ship response at an assumed confidence level has been determined and analyzed. Ultimately, the results were compared in the safety-critical cases concerning various wave and operational conditions. The outcome of this study may be found useful by all parties involved in developing maritime autonomous systems and modeling ship motions. • The impact of stochastic wave realizations on a passenger ship's response is investigated for turning maneuver. • The ship motion parameters, i.e., the maximum amplitude of roll, pitch, and lateral accelerations are analyzed. • The realizations of irregular waves are investigated concerning various environmental and operational conditions. • The simulation-based approach is utilized to determine the required number of wave realizations. • The factors influencing minimum sample size with regard to wave stochastics are investigated. [ABSTRACT FROM AUTHOR]

In times of progressive automation of the marine industry, accurate modeling of ship maneuvers is of utmost importance to all parties involved in maritime transportation. Despite the existence of modern collision-avoidance algorithms using 6DOF motion models to predict ship trajectories in waves, the impact of stochastic realization of irregular waves is usually neglected and remains under-investigated. Therefore, herein, this phenomenon and its impact were investigated in the case study of the passenger ship's turning. To this end, statistical and spatiotemporal distributions of ship positions and corresponding trajectory parameters were analyzed. This was made using massive 6DOF simulation data with particular attention to the observed extremes. Additionally, the minimum number of wave realizations has been determined using different methods in various simulation scenarios and afterward compared concerning parameters' impact and existing dependencies. The results indicate that for simulated scenarios, the required number of wave realizations should be at least 20, but in rough seas should be greater than 30. These values satisfy an acceptable and operationally reasonable error limit reaching 15% of the ship's length overall. The obtained results may be of interest to autonomous ship developers, scholars, and marine industry representatives working on intelligent collision-avoidance solutions and ship maneuvering models. • The impact of stochastic realizations of irregular waves is investigated for the case of ship turning. • The turning circle parameters (advance, transfer, tactical diameter, max drift distance) are analyzed. • The wave realizations are analyzed concerning various environmental and operational conditions. • The bootstrap-inspired simulation method is proposed to determine the minimum sample size. • The minimum number of wave realizations is determined and analyzed for various simulation scenarios. [ABSTRACT FROM AUTHOR]

Various endeavors are undertaken by the maritime industry, academia, and policy-makers to reduce greenhouse gas emissions. These include the search for feasible technologies that could be used onboard merchant vessels and are propelled by international legal and social initiatives. To this end, this study aimed to critically analyze the research trends pertaining to the active methods of reducing the negative environmental impact of shipping. The research is focused on alternative fuels and renewable energy systems with respect to the related policy-making and existing legal framework. Therefore, a bibliometric approach was applied to a sample of 234 scientific papers indexed in the SCI-EXPANDED in Clarivate Analytics Web of Science Core Collection. The results indicate that the scientific efforts were made more on alternative fuels, while renewable energy sources only recently became a popular research subject. Moreover, the environmental benefits of prospective technologies are more investigated than their financial aspects. The research effort on alternative maritime fuels was made in parallel with the legal one, both aiming to combat global climate change and magnifying each other. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

• Empirical values of Bow Crossing Range (BCR) were determined and analayzed. • A decade of AIS big data of merchant vessels was utilized. • Statistical and geospatial analyses of BCR were performed based on real maritime traffic. • Influence between BCR and ship type, dimensions, speed, daytime, and type of navigational area were investigated. Even in the era of automatization maritime safety constantly needs improvements. Regardless of the presence of crew members on board, both manned and autonomous ships should follow clear guidelines (no matter as bridge procedures or algorithms). To date, many safety indicators, especially in collision avoidance have been proposed. One of such parameters commonly used in day-to-day navigation but usually omitted by researchers is Bow Crossing Range (BCR). Therefore, this paper aims to investigate, what are typical, empirical values of BCR during routine operations of merchant ships, as well as investigate what factors impact this indicator and to what extent. To this end, a ten-year big dataset of real maritime traffic obtained from the Automatic Identification System (AIS) was used to provide statistical and spatiotemporal analyses. The results indicate that BCR is strongly related to the type of navigational area (open sea or restricted waters) but not with the dimensions or speed of ships. Among analyzed vessel types, passenger ships were noted as vessels that cross other bows at the closes ranges. Results of this study may be found interesting by fleet managers and developers of Maritime Autonomous Surface Ships (MASS). The former could utilize the results to provide revised operational guidelines for deck officers while the latter - propose an early-detection warning system based on empirical data for prospective MASS. [ABSTRACT FROM AUTHOR]

• Improved version of the Collision Avoidance Dynamic Critical Area (CADCA) is proposed for ship encounters with stationary obstacles • The CADCA concept has been improved to increase its accuracy and computation time • Modern cruise ship and post-Panamax container vessel are utilized in the simulation study • Encounters with four obstacles differing in size and shape are investigated • The impact of ship operational parameters on the required maneuvering area (rudder angle, initial speed, course alteration) is investigated In times of increased automation of maritime transportation, ship collision with a stationary obstacle (allision) remains a significant problem. There are many existing solutions rooted primarily in the concept of ship domain and path-planning algorithms. However, among these, a geometrical approach to the determination of a required maneuvering area considering the dynamic nature of ship operations in close-quarters situations is still missing. Therefore, an improved concept of the CADCA (Collision Avoidance Dynamic Critical Area) is introduced for the case of ship allision. The CADCA is a deterministic zone that geometrically delimits required maneuvering space of a vessel. Its shape changes depending on the operational parameters of a ship, such as the magnitude of rudder angle, initial forward speed, or planned alteration of the course. In contrast to ship domain, the CADCA is determined using the critical distance between two objects called MDTC (Minimum Distance to Collision). Therefore, the CADCA concept can be used to appoint a position of no-return in a close-quarters situation, so as to determine the time and distance of the last-minute maneuver. An improved method of CADCA determination is introduced, along with an investigation of operational factors influencing the ship's critical area in allision scenarios. The simulations have been conducted for large passenger and container ship in encounters with various stationary obstacles differing in size and shape. The results indicate that from the operational point of view, a deflection of the rudder is the most influencing factor on the size of the CADCA, while the impact of ship speed is negligible for the investigated vessels. Besides, various applications of the CADCA are proposed and discussed for both manned and prospective autonomous vessels. [ABSTRACT FROM AUTHOR]

This paper introduces the concept of Collision Avoidance Dynamic Critical Area (CADCA) for onboard Decision Support System s (DSS). The indicator proposed is derived via identification of a minimum required maneuvering zone in an encounter between two vessels. The CADCA model accounts for ship maneuvering dynamics and associated hydrodynamic actions emerging from different rudder angles and forward speed effects. The method presented is novel as it considers the variability of a critical area due to dynamic changes in operational parameters for both vessels. Results of the simulations carried out in negligible weather conditions confirm that computed zones may differ significantly in terms of shapes and limits. It is demonstrated that the size of the CADCA depends on the rudder angle, forward speed, as well as the dimensions of the vessels. • A concept of Collision Avoidance Dynamic Critical Area (CADCA) has been proposed. • CADCA is a required maneuvering zone determined for encountering ships. • 6DoF ship motion model has been used to simulate realistic ship trajectories. • CADCA adjusts its shape accordingly to operational parameters of vessels. • CADCA differs depending on the dimensions and characteristics of encountering ships. [ABSTRACT FROM AUTHOR]

• System-theoretic safety control structure is revisited to identify research directions in the domain of autonomous shipping. • 47 research papers are reviewed. • Results indicate that most of scholars focus on the sharp-end of the system: its technological aspects. Despite the concept of Maritime Autonomous Surface Ships (MASS) being in the limelight of research and development effort within the shipping industry, there are still some existing research gaps. These pertain not only to technical solutions to be implemented but also to the issue of the impact of new technology on maritime safety. In an attempt to identify these gaps, we perform a literature review of the operational features of remotely-controlled merchant vessels. The framework is based on a safety control structure developed in accordance with the principles of System-Theoretic Process Analysis (STPA). The results indicate that most scholars focus on the high-end components of the system, while some organizational and human-oriented issues remain under-explored. These results can be found relevant by scholars and industry partners active in the domain of autonomous shipping. [ABSTRACT FROM AUTHOR]

• More than 100 papers are reviewed concerning onboard Decision Support Systems. • Collaboration networks of authors and countries are elaborated. • Most of Decision Support Systems remain on relatively low Technology Readiness Level. • The cooperation between academia and industry in the field of Decision Support Systems is unsatisfactory. Maritime transport faces new safety-related challenges resulting from constantly increasing traffic density, along with increasing dimensions of ships. Consequently, the number of new concepts related to Decision Support Systems (DSSs) supporting safe shipborne operations in the presence of reduced ship manning is rapidly growing, both in academia and industry. However, there is a lack of a systematic description of the state-of-the-art in this field. Moreover, there is no comprehensive overview of the level of technology readiness of proposed concepts. Therefore, this paper presents an analysis aiming at (1) increasing the understanding of the structure and contents of the academic field concerned with this topic; (2) determining and mapping scientific networks in this domain; (3) analyzing and visualizing Technology Readiness Level (TRL) of analyzed systems. Bibliometric methods are utilized to depict the domain of onboard DSSs for operations focused on safety ensurance and accident prevention. The scientific literature is reviewed in a systematic way using a comparative analysis of existing tools. The results indicate that there are relatively many developments in selected DSS categories, such as collision avoidance and ship routing. However, even in these categories some issues and gaps still remain, so further improvements are needed. The analysis indicates a relatively low level of technology readiness of tools and concepts presented in academic literature. This signifies a need to move beyond the conceptual stages toward demonstration and validation in realistic, operating environments. [ABSTRACT FROM AUTHOR]

A recent publication of two independently performed studies investigating a very similar topic of green shipping, applying very similar methods (bibliometric analysis) on very similar data sets (scientific databases) provides an opportunity for an unbiased analysis of what factors can impact the outcome of one's research. This discussion paper reviews and compares the two following papers: • Ampah, J.D., Yusuf, A.A., Afrane, S., Jin, C., Liu, H., 2021. Reviewing two decades of cleaner alternative marine fuels: Towards IMO's decarbonization of the maritime transport sector. J. Clean. Prod. 320, 128871. https://doi.org/10.1016/j.jclepro.2021.128871 • Kołakowski, P., Gil, M., Wróbel, K., Ho, Y., 2021. State of play in technology and legal framework of alternative marine fuels and renewable energy systems: a bibliometric analysis. Marit. Policy Manag. https://doi.org/10.1080/03088839.2021.1969460 This paper aims to conclude on the insights arising from both papers concerning their different methodological peculiarities. • Commentary on two independent bibliometric studies on alternative fuels for shipping. • Similarities and differences of both studies discussed. • Current commentary offers key insights into the use of bibliometric analysis. [ABSTRACT FROM AUTHOR]

• Framework linking relevant and observable factors to accident susceptibility (AS) at sea are established. • Waterway, traffic and environment complexity determine navigator performance thus AS. • Domain knowledge is elicited from experts, enhanced with vast aviation experience. • Case studies covering 8 months of data reveal good correspondence of the framework with reality. The continuous monitoring and assessment of operational vulnerability and accident susceptibility of passenger ships is crucial from the perspective of ship and passenger safety. Despite the existing solutions for vulnerability monitoring, stemming mainly from watertight door operations, a comprehensive framework for accident susceptibility assessment and monitoring is missing in the literature. Therefore, this paper offers a straightforward approach, utilizing heuristics rooted in the solid foundations of the first principles related to human performance. The proposed approach allows the evaluation of accident susceptibility of a ship in operation involved in open-sea and coastal navigation. The framework presented is based on observable and relevant factors , known to affect the navigator's performance, and as a consequence accident probability. The layout of the framework as well as the parameters of the developed model are based on literature survey in maritime and aviation domains, knowledge elicited from maritime experts and extensive simulations with the use of an in-house developed ship-ship encounter simulator. Subsequently, the model is applied to selected case studies, involving two distinctive ship types, namely a large cruise ship and a RoPax vessel. The results obtained for the case study presented in this paper reveal that most of their time the analyzed ships operate with negligible accident susceptibility (87%), while 1% of the cases are labelled as very high accident susceptibility. The remaining share of 12% is distributed among low, moderate and high values of accident susceptibility. The results are in line with earlier studies conducted in the same area but adopting different methods. The proposed solution can be applied as an onboard decision support tool, evaluating the operational accident susceptibility and vulnerability, thus increasing the crew's situational awareness. Additionally, it can be applied to historical data, allowing ship navigational safety diagnosis and implementation of appropriate countermeasures. [ABSTRACT FROM AUTHOR]

Maritime Autonomous Surface Ships (MASS) have recently drawn significant attention throughout academia, governments, and industry. One of the requirements for MASS is that they should at least be as safe as conventional ships. Often, to measure their level of safety, the concept of risk is adopted, and risk influencing factors are determined. This paper proposes a framework for the identification of factors that influence the navigational risk of remotely controlled MASS without crews on board. Therein, four operational phases are considered: voyage planning, berthing and unberthing, port approaching and departing, as well as open sea navigation. For each phase, four types of factors are assigned related to human, ship, environment, and technology. To populate the framework, a thorough literature review is conducted, which is further supported by the elicitation of expert knowledge. As a result, 23 human-related factors, 12 ship-related factors, 8 environment-related factors, and 12 technology-related factors were defined. The proposed framework can be employed for any risk and safety analysis related to remote-controlled MASS. This, in turn, may assist the processes of design and operational planning of maritime transportation systems accommodating MASS and its remote-control center, e.g., the shore control center. •Risk influencing factors (RIF) for Maritime Autonomous Surface Ship operating at third degree of autonomy (MASS DoA3) is investigated. •A 4P4F framework is proposed to identify RIF on MASS DoA3, focusing on 4 operational phases and 4 types of factors. •Literature and experts' experience are utilized for identifying RIF and assigning them into 4 operational phases. •23 human factors, 12 ship factors, 8 environment factors, and 12 technology factors are identified as RIFs related to MASS DoA3 navigation. [ABSTRACT FROM AUTHOR]