This paper investigates the problem of estimating the traffic behaviors of vessels in the restricted water area. A stochastic domain around a vessel in the area, in which the navigator would maneuver his vessel with attention to movements of other vessels, is assumed, and then the vessel speed is given as linear functions of the density of the other vessels in the domain. Consequently, it can be said that the distributions of the vessel speed and the travelling-time are approximately related to the binomial distributions.