The next step: Quantifying infrastructure interdependencies to improve security

Understanding cascading effects among interdependent infrastructure systems can have an important effect on public policies that aim to address vulnerabilities in critical infrastructures, especially those policies pertaining to infrastructure security. Efforts to quantify these cascading effects and illustrative examples of such metrics are presented. The first set of examples is based upon various impacts that the 14th August, 2003 blackout in the USA had on other sectors. A second set of examples is based on various electric power outages and their impact on other infrastructure systems collected from the authors' research. Although efforts to quantify cascading effects are challenging, given the nature of the data and its limited availability, research in this area can provide useful metrics.