Environmental Engineering Reference
In-Depth Information
tradeoffs, and feedback loops that enhances the organization's ability to
monitor/revise risk models and to target safety investments. There is a
substantive difference between the world of reliability and the world of
resilience. The world of reliability (at least in the engineering domain) implies
a view that the performance of systems can be decomposed into subsystems
and components, whose reliability can be calculated and then aggregated to
provide estimates of the system as a whole. This concept underlies modeling
techniques like the traditional form of probabilistic risk (or safety) assessment
(PRA or PSA). This is deemed to be satisfactory for certain kinds of
engineered systems, at least for day-to-day operations, like nuclear and
chemical plants. That is because system components and their behavior are
treated largely as independent of one another. While this may be valid on a
day-today basis, discounting longer term influences like poor maintenance,
reductions in staffing, and so on, that can provide coupling between
components can be a serious mistake.
The world of resilience therefore requires a different approach. Here,
modeling the performance by decomposing the system to its individual
components provides very misleading results—in many cases, the results from
a decomposed model would substantively under-predict the overall
performance. Resilience represents the
coagency
of subsystems and
components hence correspond to an organic model of performance [30].
Research has shown that high reliability organizations create safety by
anticipating and planning for unexpected events and future surprises. These
organizations do not take past success as a reason for confidence. Instead they
continue to invest in anticipating the changing potential for failure because of
the deeply held understanding that their knowledge base is fragile in the face
of the hazards inherent in their work and the changes omnipresent in their
environment. Safety then becomes a value that requires continuing
reinforcement and investment. The learning activities at the heart of this
process depended on open flow of information about the changing face of the
potential for failure to guide constructive changes without waiting for
accidents to occur.
1.5.1. System Failure in the View of Resilience Engineering
In resilience engineering, failure is seen as the flip side of the adaptations
necessary to cope with the complexity of the real world, rather than as
breakdown or malfunctioning as such. The performance of individuals and
