Field Factor in the Sea Traffic Related Human Factors

摘要

This study clarifies the field factor at sea both in the daytime and at night using the distance (unit in nm: nautical mile) of the first visual perception. The field factor is defined as the luminance ratio between the luminance difference threshold and the luminance difference of the target as compared with the background luminance.The field factor in the road traffic is adjusted to 4～6 based on the result of the experimental study by Roper & Howard in 1938. However there is no study regarding the field factor in the sea traffic.In this study, the field factor in the sea traffic is based on the results in the daytime from the casualty judgement reports by the Japanese Marine Accidents Inquiry Agency (MAIA), and also the results of at night by comparing with the reports mentioned and the experimental study on the measurement of the ship's stem light.These studies are based on the investigation of the casualty reports about ship's collision and of the visibility level while examining a psychological factor necessary for the proper lookout from the navigation bridge of the ship.Finally, the field factor in the sea traffic is 2～3 whether it is in the daytime or at night.