4.1 Condition for an Occurrence of Human Insufficient Behavior

　

 It has been already found that a human insufficient behavior was apt to occur when the task was not accomplished within a given time. The given time means attainable time to accomplish the task. And influence in navigational environment has a dramatic change on the required competency. As the result of analysis mentioned above, we made a proposal that human insufficient behavior would occur when the balance between required competency by navigational environment and attainable competency by mariner will be broken, namely, when a quantity of the task exceed human competency. The concept of this condition can be formulated as formula (3).

　

　

where