Yoshiharu SAKAMOTO’s scientific contributions

We need to forge preventive measures that take into account human factors in order to prevent collision accidents. Not only are marine accidents caused by deeply concerning human factors, but many other accidents and disasters are as well. In this study, the authors studied factors that affect human elements on ship operations, and proposed the m-RSHEL Model which expands on the m-SHEL Model by expressing human factors based on the results. In addition, the authors focused attention on R (Human Resource) which is one of the important factors influencing human elements, and discovered the following results by investigating collision accidents that occurred in Tokyo Bay: 1) Personnel The competency to properly use equipment, apparatus etc. for maneuvering, as well as observing SMS and legal restrictions for navigation 2) Manning The manning of sufficient number of navigators who can fully identify and recognize other vessels to ensure safe navigation 3) Training Training that determines and carries out safe distances from other vessels for the navigators of cargo or tanker vessels

Fishing vessels' collision accidents are the most common type of collision accidents and 40% of the cause is "nonobservance of rules" and 30% is "insufficient lookout." It is necessary to figure out the generating mechanism of a navigator's unsuitable action to prevent fishing vessels' collision accidents. Authors analyzed the characteristic of navigator's collision avoiding action in fishing vessels' collision accidents by using the developmental process of navigator's errors and the model of navigator's collision avoiding action. In addition, authors interpreted the ingredient axis by using quantification method III in order to explore the background of navigator's action which resulted in the collision. The main conclusions obtained by this research are as follows. ・In fishing vessels' collision accidents, the tendency which result in collisions without correcting the error of navigators generated in early stages of avoiding action with subsequent avoiding action is strong. ・The navigator's action of fishing vessels' collision accident can explain more than 40% by the three background factors, "the attentiveness for lookout", "cognitive action", and "the circumstantial judgment of another vessel". ・In order to decrease fishing vessels' collision accident, it is important that navigators of fishing vessels understand the importance of early avoiding action.

Navigators take action to avoid the collision with other ship according to the situation awareness or movements of it. These collision avoiding actions taking by navigators are chains of actions based on the navigator's information processing system and collision accidents are occurred by navigators' errors which are happened on the navigators' information processing system, the action of other ship, and chains of theses and combined. Authors made the action model for preventing collision based on the navigator's information processing system and investigated navigators' errors which occurred in every step of collision avoiding action. Furthermore we compare navigators' actions which lead to collisions and avoid collisions safely and obtain useful information to prevent collision accidents as follows. ・ Navigators' errors are repeated in the steps of navigators' collision avoiding actions. ・ Navigators' errors are occurred in the step of "Awareness of other ship" or "Recognize other ship's movement". ・ It is important that navigators recognize other ship's movement exactly to avoid the collision. ・ Navigators aware the other ship, recognize the other ship's movement exactly, and estimate and confirm the risk of collision by several means in all cases of avoiding collision safely we investigated.

It is said that marine accident caused by human error of ship's navigator, such as mistaking to look out and unusual maneuver, accounts for about 80% of the total accidents. As the process of error caused accident is diverse, we have to research how navigator makes an error firstly. As the result, we can understand how its error causes ships' collision accidents. If we can make clear the process that navigator commits errors, we can build an effective and preventive measure against accidents. The authors established the classification method of human error on ships' collision accidents to make clear the dangerous factors behind an error based on the analysis of human error occurred in these accidents. Moreover the authors made clear the relation among factors regarding the error rising process by making use of the accident analysis using the classification method which authors had already established and reported. Last time, the authors had a grasp that the navigation under particular situation such as restricted visibility and nighttime, influences the process that navigator commits error, however could not make clear the relation between the error and the navigation under particular situation. This time, the authors conducted the error analysis by using quantification method and pointed out characteristics of the human elements in the case of ships' collision accidents occurred in restricted visibility and at night. As results of this study, following characteristics of human elements were pointed out. ・Navigators tend to make conjectures on other ship's avoiding action even if navigators realize the risk of collision in restricted visivility. ・Navigators do not tend to detect the risk of collision even if navigators realize the other ship existence at night.

It is said that marine accident caused by human error of ship's navigator in terms of mistake to look out, unusual maneuver is account for about 80% of the total accident. As the process of error caused accident is diverse, we have to research how navigator makes an error, as the result of that, how its error cause marine collision accidents to build an effective prevent measure against accidents. The authors established the classification model of human error on marine collision accidents to clear the dangerous factor behind an error based on the analysis of human error occurred in marine collision accident being included the book judging marine accidents. The authors made clear the relation among factors on the error rising process by making use of the accident analysis using the classification model which the authors established and reported. This time, the authors conducted the error analysis using Quantification Method which is one of the measures for Multivariate Analysis. At the same time the authors researched the clue of making guideline which is needed to conduct safety navigation for vessels by trying to grasp both each compositions of factor and total image of error.

The human error caused by ship's navigator can be estimated as a wide ranged subject, because there should be various internal factors and environmental factors that affect a navigator's information processing system. For the purpose of preventing from accidents, it is needed to investigate not only when and how a navigator makes error and also how the error is related to the accident. The authors have constructed and also proposed the classification model of human error on marine collision accidents, in order to analyze the causes of the accident triggered by navigator's human error and to find some hazardous factors behind the error background. Finally the authors tried to verify the availability of this classification model. In this study the authors investigated 190 marine collision accidents by applying this classification model of human error and analyzed the incidental situation of the navigators' human error.

It is said that about 80% of marine accidents have been occurred by ship's navigators' human errors, such as improper lookout, inappropriate ship's handling. To prevent these accidents, marine navigation environment which is hard to occur of human error must be developed. The human error which is caused by navigator is put on a wide range of subjects. To prevent the accidents, it is needed to investigate when and how a navigator makes error and how the error is related to the accident. It is for that purpose that the human error modeling is very important method to determine the most critical phase under the human information processing system. This study proposes the human error classification on marine collision accidents in order to analyze the occurrence form of navigator's human error and find the latent hazard factor of the error background, and then verify the availability of the classification.