The Journal of the Nautical Society of Japan
Online ISSN : 2433-0116
ISSN-L : 0466-6607
On a Method to Estimate the Probabilities of Collisions of Ships in Any Fairways
K. Hara
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1971 Volume 46 Pages 191-200


Author proposed a new method on the estimation of the probabilities of collisions of ships passing through any fairways with confused marine traffic, applying the queing theory to marne traffic and ship maneuvers. Ships are used to pass through fairways making various kind serveices such as maneuvers for altering coarse or avoiding collision to other ships and obstacles. The records of heading angle of two large tankers passing through the Singapole Strait and the Inland Sea in Japan were analyzed to get the statistical characterintics of ship's manurvers. The results show the following two points, (1) arrivals of other ships and obstacles which require services are randamon (2) the distribution of service times is nearly negative exponential. Therefore, the stationary probability of collision can be estimated by the following equation based on the queing theory P=ρe^<-μτ(1-ρ)> where: P: probability of collision ρ: the ratio of λ to μ (Collision Avoidance Intensity) λ: mean value of arrivals per unit time μ: mean value of serveices per unit time τ: limit of waiting time. The probabilities of collisions of ships passing through the Uraga strait were caluculated by this method. The values of λ, μ and τ were reasonably estimated based on the many reports of marine traffic engneering. The results of calculation were compared with the statistic value of collision and stranding there in the last ten years and the agreement between them were found to be good except for small vessels. Therefore this method is applicable to evaluate the validity of regulation and control on fairways and the imporvement ship's maneuverability on the point of the safe navigation.

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© 1971 Japan Institute of Navigation
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