In the “Action Preventing Collisions at Sea”, regardless of the type of ship, the size of the ship, and the maneuverability, the timing of “Risk of collision” is defined as “a certain point”. In addition to navigating the ship according to the navigation law, the operators take actions to avoid collisions in consideration of weather, sea conditions, ship traffic congestion, water area, and own ship maneuverability.
On the other hand, in the Japan Marine Accident Inquiry, the date of the collision is traced back to determine the timing of “Risk of collision” and the navigation law is determined. However, when we meet on each other between a low-speed small vessel and a high-speed large vessel, there is a difference in the timing of “Risk of collision”. In particular, collisions between engaged in fishing vessels and general power driven vessels have occurred constantly.
In this study, for fishermen and pilot trainee, (1) when they feel a “Risk of collision”, (2) differences in avoidance action, and (3) applicable navigation with “Risk of collision” against engaged in fishing that do not display lights and shapes; Results of questionnaire survey focusing on the above three points, It was possible to point out the problems of the current law that are different from the events in the field.
Wave disasters have been caused repeatedly since long ago by swells which are called Yorimawarinami on the coast of Toyama bay. For examples of the wave disasters, two parsons died and houses, breakwaters, etc. were destroyed in February,2008 and cargo ship REAL drifted and grounded on wave dissipating blocks in October, 2017 in Fushiki-Toyama Port. It became clear by wave generating experiments that wave heights increase twice due to beat phenomena of generated waves in a shallow water, therefore it is considered that the dragging anchors and the grounding on were caused by increasing wave heights due to the beat phenomena of swells with periods of more than 10 seconds in shallow waters.
Then we tried to observe the beat phenomena of swells in shallow water off Ebie using a marine radar and a wave analysis device from December, 2017 to March, 2018. As a result of the observation, we succeeded to catch the beat phenomena of swells by the radar system and we verified that it is possible to observe beat phenomena of swells by radar in a shallow water.
In recent years, research on autonomous ships has been conducted worldwide. The authors have also developed an automatic collision avoidance system, and have reached practical use level as elemental technology through actual ship experiments. However, there has not been enough research and discussion on the evaluation method for the purpose of certification of this automatic collision avoidance system. In this paper, we propose a method to evaluate the safety of automatic collision avoidance systems for the purpose of class certification in the future. The proposed evaluation method is based on the assumption that an automatic collision avoidance system for unmanned vessels (remote operation) does not cause anxiety on manned conventional vessels and basically follows the current COLERGs. In addition, according to the proposed evaluation method, evaluations were conducted for the purpose of safety certification using the automatic collision avoidance system developed by the authors as an example.
There are many small islands in the Seto-Inland Sea. The depopulation and population ageing of these islands have caused steady decrease in the users of passenger boat lines which connect between these islands and the mainland. Because of this, some of the lines have been on the verge of closing their services and some of them are already given subsidy from the local government in order to maintain their services. Validity of such a subsidy and an amount of it should be assessed.
The passenger rapid boat line connecting the Osaki Kamijima Island and the mainland, which is the target of this study, has been in deficit and operated by being given the subsidy from the local government. In this study, validity of the subsidy to the line is assessed by analyses of its necessity and economical valuation on the basis of the data obtained from the questionnaire survey that was carried out to the islanders.
Tokyo Bay is one of the most congested areas in the world ,where about 500 vessels come and go every day. In the past, the traffic control room of each port was located around the bay, but Tokyo Bay vessel traffic control was unified to improve chronic traffic congestion and emergency vulnerability, and it was integrated into the TOKYO WAN Vessel Traffic Service Center in Yokohama. While the number of vessels in the bay is gradually decreasing, the total tonnage of the vessels is increasing year by year, and the importance of traffic control for large vessels is further increasing.
In this study, in response to the centralization of Tokyo Bay vessel traffic control, we investigated the changes in vessel traffic in the bay using speed data by AIS and based on the actual situation of vessel traffic and vessel-land communication using international VHF radiotelephone, we proposed a more efficient vessel-land communication method to improve safety of vessel. As a result of the survey, it was found that the speed of large vessels increased, and the proportion of information provision increased due to centralization.
The purpose of this study is to establish a method that can reasonably identify the occurrence factors of the disasters and examined whether the method in this study would be an effective resource for planning safety measures for prevention of seafarer’s disasters.
The occurrence factors of seafarer’s disasters are identified by the Common Performance Conditions (CPCs) which used in the process of identifying the causes in Cognitive Reliability and Error Analysis Method (CREAM). As a result of analyzing 100 cases, we identify all the matters pointed out by the Japan Transport Safety Board (JTSB) as the causes and show the validity of this method. From the specific results, “Working in a dangerous area” is the most important factor in an accident.
The relationship between the occurrence factors is examined, and it is found that there are strong links between the 3 factors such as "organization", "environment" and "human-machine interface", and "work in dangerous areas" is central to the relationship between many factors. Based on these relationships, comprehensive measures against multiple factors can be considered, so it seems that safety measures can be examined more efficiently.
In the 2011 Tohoku earthquake and tsunami, a lot of sea disasters of ships moored along terminal inside harbor basins occurred. In order to make a countermeasure for the disasters, and investigate the mechanism of the ship’s behavior, it is required to reproduce the motions of ship precisely, and the key issue is how to express and estimate the tsunami wave force. In this paper, a physical model test on dynamic behavior of a moored ship which is a modeled 90,000DWT class coal carrier affected by the disaster, has been conducted in two-dimensional water tank during a tsunami bore. The surface elevation, current, motions and mooring loads of the ship have been measured in a following sea. The reproduction of the ship’s behavior and estimation of the tsunami wave force have also been done by using a numerical simulation method of ship motions and mooring loads.
Essential navigation rules of the KURUSHIMA Traffic Route, when current is favorable, a vessel shall navigate through the NAKA Suido Channel. Current is adverse, a vessel shall navigate through the NISHI Suido Channel. But when change of tides is expected or is occurring, KURUSHIMA MARTIS may instruct a vessel to take special passage track which different from the one prescribed in section. Therefore, by clarifying the judgment criteria and the place where the special instruction has been issued we make it possible to judge the intention of the controller early and secure the safe ship traffic in the KURUSHIMA Strait.
Recently, a great deal of attention has been focused on marine engineering research involving the combination of information technology and communication technology, leading to the development of applications such as remote maneuvering. Wireless communication properties (e.g., stability, speed, low latency, and available location) are important factors for the performance of these applications. However, the quality of these properties on the open sea is unclear. In this paper, we investigated the received signal strength and transmission speed for each LTE band at sea in order to design a multipath controlled maritime wireless communication system. We developed a device that can measure the received LTE signal strength for each band and installed it on the compass deck of the training ship “Shioji-maru”. Using the measured data, we investigated the distribution of received signal strength for LTE bands 1, 3, and 19, as well as the difference of transmission speed in each band in Tokyo Bay and off the coast of Tateyama. These results have the potential to be used for the selection of the LTE band for optimal communication performance at a given position and the form of line aggregation that can satisfy the communication performance required by the application.
In recent years, on-board monitoring has been performed widely to estimate ship performance at actual sea. To analyse monitoring data, the authors tried to make estimation models which have high predictive power and high explanatory power. At first, the authors cleaned data using reconstruction error by autoencoder. Then, the authors made estimation models using 24 neural networks and bagging to predict SHP and log speed of 2 ships. Prediction error of test data is as follows. MAPE is 1-3%, RMSPE is 2-8%, R2 score is 0.96-0.99. Also, the authors confirmed estimation models can estimate ship’s performance in calm sea and effects of hull fouling, aging and disturbance due to wind and wave. It can be said that the method proposed in this paper is effective to make the estimation models with high predictive power and high explanatory power.
This paper presents a case study of the use of and concerns with deploying small ships to support Kasado Island, Kudamatsu City, Yamaguchi Prefecture, in July 2018, after a heavy rainfall that isolated the island. Additionally, on July 7, 2018, due to the heavy rainfall, a landslide occurred on Prefectural Road 173 that rendered the only access road unpassable and a part of the island was further isolated. As part of the provision of aid, from July 9, 2018 to July 28, 2018, a marine transport operation was conducted on three routes from Kasado Island to the mainland that transported approximately 31,300 people. Thus, small ships became a valuable means of transportation that supported the rescue of residents, and thus the importance of ships was demonstrated. Information on the primary problems of this marine transport operation was collected through a questionnaire survey conducted with the island’s residents as regards the arrangement of user and health management at the port, problems with the port itself, access to the port, and consideration for unavailable residents.
Seafarer’s accident have decreased since 1967 when the official accident investigation have begun. According to a survey from 2002 to 2015, seafarer’s dead accident about 10 cases per year and accident that take more than three days off work 309 cases. Further, seafarer’s all accident is about four to five times high rate as compared with the disaster rate of all the industries on land at present.
In this study, authors investigated the seafarer’s accident for the 14 years, have grasped the work during a accident between that off work days of the accident. Quantitative risk assessment was used to determine days lost and work accident.
In this paper, quantitative risk assessment was applied to seafarer’s accident, and the main conclusions obtained by this research are as follows.
(1) Ocean vessels work accident are high risk due to maintenance and management of machinery.
(2) Coastal vessels (more than 100 employed seafarer’s) are high risk due to cargo handling.
(3) Coastal vessels (less than 100 employed seafarer’s) has high risk due to maintenance and management of machinery.
Ships are more difficult to automate than other vehicles. This is because they are exposed to disturbances such as tidal currents, waves, winds, etc., and their dynamic characteristics fluctuate greatly during the voyage. To date, autopilots have become popular for assisting voyages. However, there are various issues in its complete automation. For example, in a questionnaire regarding the disadvantages, there are answers that "they are susceptible to the tide" or "the displacement due to disturbance cannot be corrected". In this study, an online system identification method is designed. Specifically, the system parameters of the hull motion model are updated only when the error of the turning angular velocity between the ship and the estimated hull motion model exceeds a reference value. At that time, after a rough local linear approximation model is designed using a database, the finish is adjusted using machine learning by particle swarm optimization. Finally, the effectiveness of the method is quantitatively verified by simulation using the input and output data of the ship.
Obstacle zone by target (OZT) is a sea area with the possibility of collision with target ships. Collision avoidance of that area will be realizing a safe navigation. Now, many ships do not avoid target ship using OZT, but we expect to apply the collision avoidance system by a distance to OZT calculated of actual ship's OZT.
In this study, 13 sea areas are set at the semi-congested waters near Mikomoto-jima, Izu-Oshima and Tokyo bay entrance, and the distribution of OZT which occurred at every sea areas is analyzed.
The distribution maps are constructed by the ship's heading distance and an occupation angle by OZT, and the features every waters are shown by maps. The distribution that have the peak by ship's heading distance is confirmed, it may be considered the starting time of the collision avoidance action.
In most sea areas, it is confirmed that the peak is 3miles at ship's heading distance, and the distribution decreased suddenly near the 3 miles. It is suggested that ships have any action for collision avoidance when OZT confirmed at ship's heading distance is 3 miles.
Data analysis regarding resources management have gained an important role between companies all over the globe in recent years. Business activities aim to profit by making an effective and efficient use of those resources, whether human or physical or financial or logical resources. New technologies such as IoT and Big Data have particularly become widely used in this matter. In this study, one-year daily report by transfer crane from August 1st, 2017 to July 31st, 2018 in the Island city container terminal in Hakata port, which includes big data, approximately 1,020,000 container cargo handling operations, are analyzed in order to comprehend the container storage status, re-handling status, utilization rate of transfer crane, and so on. Some methods for situation analysis of the big data on the container cargo handling operation are considered.