Network Design and Traffic Control for Reducing the Probability of Multiple Encounter of Ships

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Both the decrease of navigational waters and the increase of pleasure boats which derive from the recent progress of coastal zone utilization in congested waters carry more dangerous situation in ship traffic. Under such a situation, a multiple encounter, the situation that more than three ships simultaneously encounter in each other, is focused as a quite dangerous situation leading to a collision, because no navigational rule to resolve the situation exists.This study aims to reduce the occurrence of multiple encounter of ships from a view point of maritime traffic engineering. The proposed procedure to find effective counter measures to reduce the occurrence of multiple encounters starts from collecting traffic and network data concerned, and involves following models and techniques :(1)a technique to grasp the present situation of occurrence of multiple encounters,(2)a simulation model to estimate the future distributions of headway and sailing course of ships on the network after changed.(3)a mathematical model to calculate the probability of occurrence of multiple encounters under the changed network,(4)a simulation model which gives us useful information on ship traffic control to resolve multiple encounters.Through the model development and its examination, some interesting knowledges have been found, which include :(1)Both unifying and dispersing links of a navigation network gives the increase of the probability of occurrence of multiple encounter. This tendency suggests the existence of optimal link density of a navigation network.(2)The water area where multiple encounter often occurs depends the types of multiple encounter such as those with and without rule conflict in collision avoidance.The models and techniques mentioned above are arranged into "A systematic procedure to reduce multiple encounters of ships by network design and traffic control".