Over the past century, our nation has experienced dramatic changes in demographics, and existing sociotechnical systems have become more complex and increasingly networked. To complicate matters, our cyberphysical infrastructure has not been maintained, causing unexpected vulnerabilities and cascading failures (ASCE, 2009; AWWA, 2001). As extreme events frequency and magnitude of resulting disasters have increased, emergent behavior, unexpected performance response, and lack of resilience have been noted (Sanford Bernhardt and McNeil, 2008). While there is success in modeling complex response and predicting behaviors of our urban sociotechnical networks under stress, the models have grown so complex that data is not available to validate the model predictions (NRC 2009).

It is clear that we need to understand our sociotechnical system dynamics and resilience at a fundamental level. We define resilience as the ability (sufficient capacity and/or flexibility) of a system to experience unexpected shocks or perturbations, and to respond and recover functionality at some acceptable level of performance or action. We have an urgent need for improved understanding of the genesis and evolution of resilience, in particular in urban transportation systems. This will allow us to build and enhance social and ecological capital and community resilience, as well as to increase system adaptive capacity (including self-organization) and improve the cost-effectiveness of investments in infrastructure systems.

An interdisciplinary approach is needed that captures attributes of the complex systems in a region. This requires assembling varied and deep information reflecting current and future conditions, response and usage so that we can expand our knowledge and validate our discoveries and predictions for system performance response. We need to assemble and create information and modeling resources, develop a framework of variables and relationships that will support a cross-disciplinary and cross-sector exploration of resilience, and build knowledge as we develop and test theory and models. In the long term, this will allow us to answer important questions including:

1. What observations (evidence) can we make (identify) to indicate qualitatively whether a specific system or network will demonstrate resiliency?
2. What metrics can be used to evaluate the capacity of a system or network for resilient response?
3. How does resilience response develop, and what factors control or influence the development? Is it a process with thresholds, tipping points, state changes, or is it a continuous function?
4. What can we understand about when investment or adaptive management is warranted to improve resiliency of a system or networks of interdependent systems?

The research proposed here will focus on identifying the basic metrics and models that can be used to develop representations of performance response that can be used to define resilience in urban environments, and to bring together data resources that can be investigated to understand and validate the interactive behavior of our complex transportation infrastructure systems.