In Japan, various kinds of methods for marine traffic simulation have been developed. Of these, network simulation is widely used for port and harbour planning
and for marine traffic planning because of its simplisity and effectiveness, especially when simulating marine traffic in large water areas such as in Osaka Bay for the Kansai International Offshore Airport project, and in Tokyo bay for Tokyo Bay Transbay Bridge project, etc. This repo rt introduces the outline of the nwework simulation.
　The simulation system is composed of the 3 parts, of the input part, the simulation process part and the output part. According to the purpose of simulation, many network simulation alternatives are developed by adding other functions. How to evaluate the project according to the results of the network simulation is also described within.