The thinking faculty and operating ability of ship operators tend to be affected by their mental task loads under the pressures from navigating environment. The suitable navigation support system has to be considered the relation between incidence of human errors and tensional stress degree of operators during ship navigation. For clarifying an issue of tensional stresses for task loads of ship operators, this paper describes that the tensional stresses were analyzed quantitatively by measuring the heart rate variability under mental work-load during navigations of several car-ferries, and the suitable measures were examined in order to reduce the work-load and the incidence of human errors caused by the task with high-tension under severe navigation environment.
The man-machine systems for marine safety, such as a ship navigation system, should be designed to consider the fact that the thinking faculty and operating ability of ship operators tend to be affected by their mental work-load under the pressures from navigation environment. A methodology for the risk assessment is desired highly to establish to prevent from occurring marine accidents originated in human factors (Fukuchi and Shinoda,2003). The suitable safety measures have to be taken properly to cope with operator's behavior based on psychological intelligence process along the state-transition during operating the man-machine system, such as a ship maneuvering apparatus (Fukuchi,2004). (Fukuchi,2000) For establishing the suitable navigation support system, it needs to consider the relation between degree of tensional stress and human errors of operators during ship navigation.
It can be found that the assumption way of tensional stress by measuring the heart rate variability is so useful to design the supporting system for prevent from occurring human errors of operators during ship navigation.
