海上交通事故の危険度と確率

<p>Marine traffic accidents in Japan are investigated here with a data base in five years from 1978 to 1982 on traffic accidents and that on traffic quantities, e.g., traffic volume and its diurnal change, the density, and the speed distribution, intending to obtain more accurate values of the accident probability and to observe time variation in the accident risk.</p><p>The risk is defined here as the number of accidents per passage and it may change largely with variation of state of traffic. The probability, P, on the contrary, may stay considerably unchanged, which is difined here as the ratio of the number of accidents, N, and that of the geometrical accidents, Ng. Ng is the number of accidents assuming that all vessels navigate without paying any attention to other vessels and obstacles. Calculation with traffic quantities allows a stable and precise estimation of Ng.</p><p>Results show considerable decrease in the collision risks in ports compared with those in early 1970's. However, risks in staits which have shown a large decrease in 1970's, show little decrease,.</p><p>Following values are obtained for probabilities of accidents:</p><p>Log P=-4.0 for collision of sailing vessels,</p><p>Log P=-4.7 for collision of vessels and fishing boats in operation,</p><p>Log P=-3.7 for grounding and</p><p>Log P=-3.7 for collision of vessels and buoys.</p><p>Above values are more reliable than previous values since the numbers of accidents are larger and a precise estimation of Ng has been made with detailed results of traffic observations. The differences between new and old values lie within a factor of 10^±0.4</p>