Infrastructure Interdependencies - - Type of Failure

Interdependencies increase the risk of failure or disruptions in multiple infrastructure.  Interdependencies can create such things as reinforcing feedback loops that are self-enhancing, leading to runaway collapses over time.  Remember that if A causes B, it is possible that B also causes A - - and the relationship does not just have to be linear.  It can be exponential.

We classify interdependencies-related disruptions or outages in one of three ways:

1. Cascading Failure - - This occurs when a disruption in one infrastructure causes the failure of a component in a second infrastructure, which subsequently causes a disruption in the second infrastructure.  An example would be a natural gas line failure that results in shutting down an electric utility's generating unit.
2. Escalating Failure - - This occurs when an existing disruption in one infrastructure exacerbates an independent disruption of a second infrastructure, generally in the form of increasing the severity or the time for recovery or restoration of the second failure.  An example might be a storm that damages the telecommunication network - - and repair crews are delayed due to flooded highway system.
3. Common Cause Failure - - This occurs when two or more infrastructure networks are disrupted at the same time: components within each network fail because of some common cause.  An example might be rail derailment that damages tracks that also cause communication and power line failures within the same corridor.