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for achieving an integrated level of reliability. It is not enough to verify each
equipment failure. By starting from the evaluation of the entire system, it
can become clear which equipment has problems.
3.3
Importance of reliability management
It is necessity to analyze risk in the course of improving safety and putting
those analyses into writing at each stage of the life cycle.
Risk management is concerned with safety. (Risk=Severity level of hazard
consequence, not frequency of train delay occurrence.)
In the analysis of risk through RAMS, risk management is carried out by
finding safety risks from “frequency of occurrence” and “resulting severity”.
We apply a reliability level instead of a risk level to the ongoing systems'
evaluation.
We believed that this applied to the stability of train service.
When applying RAMS analysis to equipment reliability, one may con-
sider “total delay time” (the sum total of delays in operation resulting from
defective equipment) as a parameter indicating “resulting severity”.
We have also considered passengers complaint as an appropriate param-
eter.
Fig. 3. Example of reliability evaluation and acceptance.
3.4
Method of analysis
We analyzed the data of malfunctions of signalling operations over the last
three years within the JR East service area.
Systems down such as those which occur when a system stops working do
not have as much impact thanks to the dual system. If one of the two systems
down, the other system continues working and thus does not inconvenience
customers.
1. First step.
The failure data for the past three years was classified as shown by the
following table.
