抄録
In the face of very complex industrial systems it is important to improve the system reliability. What matters is not to design a system which will never be in disorder but too expensive, but to design those machines which are reliable enough for the given environmental conditions, and to have derating or fail-safe functions for disorder cases. Human error probability should then be lowered through ergonomic measures. Quantification of human factors which are to be considered inn the system design is urgent for the optimum judgment.
