An additional fact is that there are many fishing vessels in the waters in this sea area. Vessels also come and go fromthe ports of Wakayama and Komatsushima, meaning that this sea area can be described as being congested. The pointwhere pilots who navigate Osaka Bay are taken on board is about 1.5 nautical miles from the Tomogashima Strait. Inorder to board the pilots who will navigate the Osaka Bay, many vessels have to slow down and prepare the engines(S/B Eng.). It may be because of this that, vessels in the area have to change heading course broadly in order to avoidcollision in these, as mentioned above, congested sea areas. This causes a disruption to the whole sea traffic system (asthe same would happen in the case of a motor vehicle changing lanes suddenly).