抄録
There are some safety assessment, some of them are inherent safety and probabilistic
safety assessment. But, it has not clearly defined of them. This paper reports the difference of both
safeties and the way of realizing optimization of Life Cycle Cost of Safety Related System. And
it proposes the concept of Safety Cost and reports it on the Railway transmission systems．About
the railway systems, the cost loss is fewer than the more safety transportation facilities in signaling
systems. So it is important to identify the concepts of the inherent safety and the Safety Cost must
need to validate it by the Risk Assessment.
