This chapter discusses the process of systematic accident prevention, which incorporates those tools, is introduced in order to reduce the number of marine accidents and incidents, resulting in safer seas with fewer accidents. It shows how the difference of occurrence mechanism between an accident and an incident will work and appear as events and contributing factors. In case of the AUTO BANNER and SHIMAYUKI incident, the SHIMAYUKI was heading to an accident trajectory. The AUTO BANNER was altering her course to starboard along the passage; the pilot felt doubt about the movement of the SHIMAYUKI when he saw the SHIMAYUKI altering her course to port by judging from the change in appearance of navigation lights. The master of the SHIMAYUKI stated that the two short blasts sounded by the AUTO BANNER convinced him of the movement of the AUTO BANNER.