When designing new marine traffic routes, it is desirable that the congestion due to traffic volume is evaluated by theoretical traffic capacity or by traffic simulation. Most of these techniques are applied to single server which is not considered channel width. Over-taking or paralle sailing of two or more vessels is allowalbe in Dover, Uraga, Gaduk-sudo, etc under their traffic capacity. In this paper, the Bumper Model is introduced to multiple severs in narrow channel and applied to Uraga Channel in Japan. The minimum width of Uraga Channel is 1, 400 m and its design traffic capacity is evaluated 19.26 ~ 19.52% of the basic traffic capacity. The traffic capacity on Gaduk Channel according to Busan New Port Development in 2011 will be estimated 3.59 % of maximum density and equal to 18.6% of that on Uraga Channel in 1992. The channel width Gaduk-sudo is designed 1, 600~2, 460 m and evaluated safe enough.

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