Public Infrastructure Service Flexibilityfor Response and Recovery in theAttacks at the World Trade Center,September 11, 2001Rae ZimmermanInstitute for Civil Infrastructure SystemsWagner Graduate School of Public ServiceNew York University___________________IntroductionAfter the terrorist attacks on the World Trade Center in New York City onSeptember 11, 2001, the ability to rapidly restore transportation, power,water, and environmental services to users was absolutely critical, especiallyto those involved in the immediate search, rescue, and recovery operations.What better way could infrastructure serve its users—both emergencyworkers and the general public—than to be able to respond quickly in acrisis? The ability to provide these services required a degree of flexibility,often unanticipated and unplanned, that only became apparent as the responseefforts unfolded. The capability of basic infrastructure service providers to respond topublic needs for transportation, energy, communication, water, sanitation, andsolid waste removal after the September 11th attacks was to a great extentinfluenced by the flexibility of the initial infrastructure design andmanagement functions to respond to normal system disruptions and toextreme, but not necessarily terrorist-related, events. The Concept of Flexibility: Definitions and SignificanceThe ability of physical systems and human services to respond rapidly to userneeds is a broad measure of flexibility, and is the focus of this paper. Theconcept of flexibility as used in this research encompasses both the flexibilityof physical configurations and the flexibility of social institutions to bringInfrastructure Flexibility in the World Trade Center Attacks242about changes that enable a system to return to its existing state or to animproved one.What makes flexibility difficult to define precisely is that it can dependon specific objectives as well as the broad social and environmental contextsin which those objectives play out. Attributes of flexibility as applied toinfrastructure services may differ, for example, when the objective is to resistfailure or survive shock as opposed to when the objective is for systemimprovement, such as expansion, in a non-crisis environment. Flexibility is often related to or associated with other traditional ortechnical concepts such as resiliency, robustness, redundancy, diversity,adaptability, and interoperability. These are described extensively in thescientific and engineering literature (for a brief summary and references seeZimmerman, 2001). Redundancy is a concept that is often consideredsynonymous with flexibility, although it is but one component of it.Redundancy has been defined in the context of the physical aspects ofcommunications infrastructure as “having extra capacity available, generallyfrom more than one source” (U.S. General Accounting Office, 2003, p. 92).Diversity, another related term, “involves establishing different physicalroutes . . . and using different equipment along those routes . . .” (U.S.General Accounting Office, 2003, p. 92).Flexibility, as used in this paper, is broader than (and encompasses) theseother concepts, giving greater emphasis to the socioeconomic, political,organizational, and environmental contexts of infrastructure systems and itsexplicit interdisciplinary character. In its most general construction, flexibleinfrastructure supports behavior that does not compromise the goals of theusers of the service and includes the ability to change or adapt. An operationaldefinition of the concept of flexibility is provided below in terms of criteria.Research ObjectiveThe research objective underscores the importance of building in flexibilityearly in infrastructure decisions. The research hypothesis is:If the initial design and operation of an infrastructure service isflexible in dealing with user needs, it will be flexible in reducing theadverse consequences of a crisis.Methods and ProceduresZimmerman (2003b) evaluates many specific measures for infrastructurecharacteristics and behavior with respect to user needs before, during, andafter the September 11th disaster at the World Trade Center. These measuresare used to test the hypothesis that flexibility supports the performance ofZimmerman243infrastructure in crises if it is incorporated as a basic or fundamentalcharacteristic of infrastructure services. Infrastructure as used in this researchencompasses transportation, energy, communication, water supply,wastewater treatment, and solid waste management services.Criteria to Characterize FlexibilityIn order to operationalize the concept of flexibility for infrastructure services,several guiding principles or criteria are used to identify and characterizeflexibility as it applies to infrastructure services. These criteria provide onebasis for designing measures to evaluate how the infrastructure performed onand after September 11th. The criteria below apply primarily to systemsfacing crisis conditions.The first criterion is the existence of alternative routes to build newcapacity or redistribute existing capacity between the sources of productionand the intended users (including emergency workers) whose services havebeen curtailed or otherwise diminished as a consequence of an extreme event.A corollary to this is the existence of alternative production facilities andlocations as well that permit production to be rerouted or otherwisesubstituted in an extreme event. The second criterion is managerial and organizational capability andcapacity to quickly identify, acquire, and manage resources needed for thesafety and security of the population, including knowledge of how thosesystems operate and the power to control them in a crisis. It includesmaterials, labor, and supplies for construction as well as to support workers,residents, and business operations. In the management literature theseresources are often referred to as “slack resources” (Pfeffer and Salancik,1978, p. 275), that is, extra resources that can be mobilized when needed. Thisability is usually considered an important characteristic of disastermanagement.Third is the ability to transfer information to users about the state of thesystem and the alternatives available to them in a way that is simple to use,easy to understand, and can be rapidly disseminated in order to reduce theconsequences of a crisis that are specifically related to infrastructure.ApproachThe approach consisted of the