RIASSUNTO
Shipping industry plays a vital role in world trade. Especially in Japan, where the land is surrounded by the sea, it carries more than 99 per cent of the volume of trade. Besides international and domestic transport, commercial fishing is one of the main industries in Japan. Major harbors, seaways, and their surrounding areas have high traffic density, and thus the risks of marine accident are not negligible. In this paper, we look into typical cases of collision casualties in middle congested areas outside traffic controlled areas, and discuss how systems can support mariners in collision critical situations. Collision casualties are analyzed from a perspective of encountering types within the traffic environment. According to the types extracted here, cognitive process analysis is then presented. Requirements for each type of collision are also discussed.