Pathways analysis is the evaluation technique used to model the security system. It involves breaking down each step of the adversary's pathway from offsite until reaching the asset being protected. Each step corresponds to the adversary overcoming a security element (either a detection or delay element) and the corresponding detection probability or delay time.

Along each pathway, the metric used to determine the
effectiveness of the physical protection system is the probability of interruption
(P_{I}). This is the probability that the security system
successfully detects the adversary attacking along the given pathway so
that the response force is
able to successfully engage the adversary and prevent completion of the
intended task. Once the adversary is interrupted, the probability of
neutralization is used to determine the probability that the adversary is stopped. These two
values are then used to determine the system effectiveness of the
physical protection system (P_{E}) for that pathway.
Substituting these values into the conditional risk equation
yield:

Rc = ( 1 - PE ) * C = ( 1 - PI PN ) * C

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