social implications of infrastructure network...

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Social Implications of InfrastructureNetwork InteractionsRae ZimmermanPublished online: 04 Aug 2010.

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Social Implications of Infrastructure Network Interactions 97

Social Implications of InfrastructureNetwork Interactions

Rae Zimmerman

resources and services for transportation, energy, communications,water supply, and wastewater collection and treatment. In large part,the increasing spread of population settlements at the periphery ofcities and the increasing density and vertical integration of urban coreshave increased reliance upon the connectivity that these networksprovide. These infrastructure networks are, in turn, dependent uponone another, both functionally and spatially, in very complex ways,and that interdependence is increased as new capacity-enhancinginfrastructure technologies are developed. The extent of these depen-dencies appears to be escalating, and that results in interactionsamong the systems and produces effects upon environments that aredifficult to predict.

Integrating these services can improve the performance of theinfrastructures, lower investment costs, and improve urban lifestyles.However, although some spatial and functional coordination of thesenetworks has occurred, the rapid growth in their deployment, ad-vances in network technology, and changes in the distribution of thepopulations the networks serve, continue to create disruptions in theinfrastructure systems. These disruptions occur, for example, in the

Journal of Urban Technology, Volume 8, Number 3, pages 97-119.Copyright © 2001 by The Society of Urban Technology.All rights of reproduction in any form reserved.ISSN: 1063-0732 paper/ISSN: 1466-1853 onlineDOI: 10.1080/1063073012011383 1

URBANIZED and soon-to-be urbanizing areas are increas-ingly dependent upon infrastructure transmission anddistribution networks for the provision of essential public

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Journal of Urban Technology/December 200198

form of street congestion, electric power blackouts, and outages ofcommunications systems to the point where major public serviceshave been disrupted with considerable social implications. Oneoutcome is the unpredictability of accidents, lending a whole newmeaning to the famous old movie title “When Worlds Collide”!

In the United States, these interdependencies have, typically, notbeen studied closely. That is changing. The U.S. Department ofEnergy (U.S. DOE) and the Office of Science and Technology Policy(OSTP), for example, underscored the importance of interdependen-cies as a critical issue in infrastructure reliability. Their report noted:

The issue of interdependencies among critical infrastructures isa fundamental dimension of critical infrastructure protection.Relative to other infrastructure-specific concerns, infrastruc-ture interdependency has been the least-studied and is probablyin the most need of more comprehensive research (11).

The U.S. DOE/OSTP report attributed the previous lack offocus on interdependencies to the interdisciplinary nature of theproblem and the lack of integration across various interest groups andstakeholders. As such, the analytical capabilities in understandinginfrastructure interconnections and interdependencies have not beendeveloped to a point where their interactions can be easily managed.One reason for the complexity of these interdependencies is the manycombinations and metrics used to characterize either the interactionsor their impacts, and analytical models to simulate these conditionshave not yet been developed. With respect to the absence of modelingcapability, the report noted, “Although some programs have exploredcoupling two or three infrastructures, there are no known initiativesdeveloping comprehensive, coupled models of four or more infra-structures” (11). Thus, even if the problem is acknowledged, the toolsare not there to address it.

Interdependencies occur at many different levels within theorganization of a system. They occur among components withinspecific infrastructure facilities, within and among specific infra-structure areas (e.g., energy, transportation), and among those areasand social and environmental systems affecting users of the serviceand communities that host the facilities. The increasing dependencyupon information technologies to manage communications and op-erations at these interfaces, in many cases, exacerbates problems. Butthese same technologies offer the promise of reducing the adversesocial effects of these networks by providing greater communicationamong the systems. Planners, then, can respond to the potentially

Perrow

U.S. Department of Energy

U.S. Department of Energy

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adverse social and environmental effects of system interconnectivityand interdependencies by relying upon redundancy—a traditionalengineering principle—and by building knowledge systems that arebased on, and reflect, the infrastructure needs of communities andindividual users.

This paper outlines three key points relating to the issue of theinteractions between and among infrastructure networks:interconnectedness and the avoidance of error propagation; redun-dancy and alternative choices in maintaining operations; and systemknowledge that allows for the detection and recognition of threats.

Although these concepts appear to emphasize highly technicalaspects of networked infrastructures, they nevertheless have impor-tant social ramifications. This is so because technological changeshave improved the provision of services of transport, water, electric-ity, and communications, often transforming the way we live, while atthe same time, substantially increasing the fragility and vulnerabilityof these systems and the service they provide by making them morecomplex and interdependent.

Interconnectedness and Avoiding Error Propagation

Interconnectedness refers to a formal linkage between two differentsystems. Graham and Marvin citing the work of Gokalp and Easterling(“Interchange and Container” and Organization Space) underscorethe inevitable interlinking of networked infrastructures, which isparticularly the case when newer systems are introduced into olderinfrastructure networks: “Only very rarely do single infrastructurenetworks develop in isolation from changes in the others” (30).

Interdependencies are a natural part of infrastructure design andoperation, but can be a source of a much wider scale vulnerability ordisruption than any single system. “The interdependence of criticalinfrastructures also enables disruption to propagate” (19). Propaga-tion means that more than one system feels the impact, often in adomino effect.

Hauer and Dagle commenting on the interrelationship of com-ponents within power systems note that:

As a system increases in size, or is interconnected with othersystems nearby, it may acquire unexpected or pathologicalcharacteristics not found in smaller systems. These character-istics may be intermittent, and they may be further complicatedby subtle interactions among control systems or other devices (22).

Mitchell

Graham and Marvin

Schneider

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As a result of the attack on the World Trade Center, infrastruc-ture was destroyed largely from physical impact on structural ele-ments. However, the cascading effects created by interdependenciesmagnified the damages within certain systems. For example, theinundation of many infrastructure systems by water contributed to thedestructive influences of the physical damage. Water originated frombroken distribution lines and from fire fighting and was a majorcontributor to the destruction of the transportation system (i.e., theflooding of train lines) and the electric power systems, which in turndisrupted telecommunications by incapacitating Verizon’s backupgenerators, AT&T’s telephone switching equipment, and the high-speed Internet transmissions provided by nearby “telecom hotels.”

Infrastructure can be interconnected functionally and spatially.Functionally, infrastructure systems can be dependent upon oneanother operationally, e.g., one system activates the other. Spatially,as infrastructure becomes more dense and compact and as distributednetworks occupy the same conduits in cities, vulnerability to break-ages can increase.

Functional InterconnectednessExamples of error propagation due to functional interdependencyarise in the context of accidents. For example, a failure in a telephoneline can go beyond disrupting the telephone service to disabling airtraffic control that depends upon telephone contact. Stock exchangefunctions and other systems dependent on telephone systems can alsobe affected. This actually happened in January 1991 in the northeastUnited States when Newark Airport ground to a halt when a backhoeruptured a fiber optic cable. In another incident, the air traffic controlsystem at Ronkonkoma, Long Island broke down on May 7, 1999when interface problems between IT hardware and software updateswere being made for Y2K compliance. Many railroad accidents haveoccurred or have had more serious consequences as a result of afailure of communication systems informing operators of impend-ing problems.*

When systems interact or interconnect functionally, the likeli-hood of failures increases for a number of reasons. One is thatdifferent systems have been developed at different times, and oldersystems often have a more difficult time adapting to newer technolo-gies. This is particularly acute where rapidly evolving informationtechnologies are involved. Supervisory Control and Data Acquisition(SCADA) systems used widely both for the detection of the conditionof infrastructure distribution lines and as a basis for operating them,often have to adapt to rapidly changing information technologies

Schneider

*These are documented in theextensive reports of the NationalTransportation Safety Board onrailroad accidents.

Guernsey

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before they need to be upgraded. Straayer, for example, points outthat, “The average lifetime for most industrial SCADA equipment isover 10 years, but networking technology changes much faster thanthat” (26).

Another more fundamental reason for failure of functionallyinterconnected systems is the lack of timing of different infrastructureactivities (such as maintenance or construction) at the same site,coupled with the absence of knowledge of the location of infrastruc-ture facilities and structures. Schneider has pointed out that backhoeaccidents are among the largest cause of failure in telecommunica-tions infrastructure lines. The mapping of infrastructure in order tomark where structures are located is critical to avoiding many of theaccidents and ruptures that occur during construction. Although themapping problem is to some extent technical, it is also political inthat different organizations may not want to share this informationfor reasons of competition and the need to protect their systemsfrom sabotage.*

Dependencies and the interconnectedness of electric power withother infrastructure systems is as pervasive as the growinginterconnectedness between information technologies and infrastruc-ture. The California electric power crisis, when it first began, resultedin the temporary shutting off of the water pumps that serve LosAngeles. Vulnerabilities can be particularly acute in times of naturaldisasters, especially where systems are centralized. For example, asMileti recounts, the high degree of centralization within the electricpower grids serving the San Francisco area contributed to the largenumber of service outages that occurred during the 1994 Northridgeearthquake “when 3.1 million customers lost electricity and close to100,000 homes and businesses were without power for over 24hours” (59). Thereafter, notes Mileti, the grid gradually becamedecentralized with greater reliance on renewable systems.

Spatial InterconnectednessIt is largely by design that distribution lines from different utilitysystems are in close proximity to one another. Historically, utilitiestook advantage of their common rights-of-way and transportationcorridors to locate utility lines. Most recently, the necessity to co-locate utility lines has been driven in part by the sheer magnitude ofgrowth in fiber optic cable for telecommunications infrastructure and,to a lesser extent, by the needs of other utility lines. Many estimatesexist of the extent to which utility distribution lines are already beinginstalled and are projected to be installed. Stix observes that, “Everyday installers lay enough new cable to circle the earth three times”

*Insofar as the ability to mapinfrastructure has been a technicalproblem, it is being addressed by

newer technologies in the form ofgeographic positioning systems and

more sophisticated computers tosupport Geographic Information

Systems. A number of cities, suchas San Diego, Los Angeles, and

New York, have now successfullymapped or are in the process of

mapping most or all of theirinfrastructure. The ability to release

that information, however, isconstrained by security concerns on

the part of municipal officials andowners of the facilities.

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(81). Iseley and Gokhale noted that about 150,000 miles of cables andservice lines are laid each year in North America—24 percent will betelecommunications (the smallest size cables though) and between15-20 percent each of gas, electric cable, water, and sewage linesaccount for the rest. Street disturbances account for a substantialamount of the cost of laying underground networks—one contractorindicated that excavating streets accounts for 70 percent of the cost oflaying fiber optic cable. Nunn estimated that in 1995 the constructionof telecommunications distribution lines was 25 percent of non-highway infrastructure.

Other estimates are more local and are drawn from practicalexperience. Estimates of the number of utility cuts for Washington,D.C., for example, were 5,000 in 1996 and 6,683 in 1998. Undergroundspaces are becoming crowded and scarce as a result of this demand.

Spatial interconnectedness of infrastructure distribution lineshas been increased by placing distribution systems underground. Thispractice has, in part, been driven by economics, with undergroundlines reportedly less expensive than overhead lines. It has been moreeconomical to share utility cuts or rights-of-way than to createindividual ones for each utility system. The practice of“undergrounding” is very old. In the late nineteenth century, numer-ous franchises were granted in New York City for laying electricallines in street cuts, at a cost of a penny per linear foot, which probablyled to chaotic street scenes during construction, not unlike whatoccurs today.

These installation sites are in close proximity to user residencesand areas in which they conduct their activities. For example, onewriter observed that “Ninety-five percent of BellSouth’s Atlantacustomers live within 12,000 feet of fiber-optic lines.” The increasein the rate and intensity of construction is now well known. The extentto which this is occurring has been so great that some cities are takingdrastic measures such as imposing construction moratoria or fees toprevent or restore damage to other infrastructures. The recognition ofthe negative effects of street openings for utility construction andreconstruction has led to an active literature on how this is being managed.A few examples of management mechanisms are offered below.

Moratoria. Social disturbances have occurred to such an extent thatWashington, D.C. imposed a moratorium between March 27 andApril 8, 2000 on laying underground fiber, pending a more unifiedplan from the nine contractors with permits. This is not the first timesuch a moratorium was imposed in the city. Reactions fall on eitherside of the issue. On the one hand, the number of times streets are

Finkelstein

Layton “D.C. Official...”

Gerwig

Miller

Brister

Tighe et al.

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disrupted for laying utility lines due to a lack of coordination resultsin business losses and social disruption. On the other hand, businessescomplain that if construction stops, layoffs will occur, the need ofbusinesses for cable lines will not be met, and the city will lose feesand other benefits from the construction.

Permit Systems and Fees. Different kinds of fee structures are usedor are currently under consideration to encourage sound undergroundconstruction practices such as damage fees (for damages to otherutility lines), access fees, and right-of-way fees. Washington, D.C.has used rental fees, with a pay schedule that is a function of thelocation of the pipe. Although such fees provide funds for municipali-ties to restore damaged transportation infrastructure and for trafficmanagement functions in connection with the excavations, they donot directly address the social disruption associated with the fre-quency and persistence of these activities. Minneapolis also has a feesystem, based on installation and repair costs and assessed on a perlinear basis. Permit systems, often coupled with fee structures, arebecoming a common means of managing network installations.Gerwig comments on the very large number of such permits, indicat-ing that, “The rule of thumb these days is that building a networkrequires about one permit per mile from a private landowner or agovernment body. . .,” accounting for about 20 percent of the cost ofa new network.

Combined Functional and Spatial Interconnectedness: The Caseof Wireless CommunicationWireless communication exemplifies the effects of both functionaland spatial interconnectedness. Functionally, different vendors in theUnited States have incompatible transmission signals. This eitherproduces variations in coverage for users across different parts of theUnited States and the world by different vendors or a proliferation ofwireless towers constructed by each of the vendors attempting toserve their own customers. Wireless transmission has producedsignal interferences in dense areas. Sanberg, for example, pointed outthat wireless devices using radio waves in the 2.4 gigahertz band areblocking each others’ transmissions. Wireless transmission can alsointerfere with electric power transmission and aircraft navigation.

The explosive growth in the number of wireless users (subscrib-ers) alone has led to a parallel growth in the number of cell sites,attesting to the spatial dependency of wireless. These growth trendsare shown in Figure 1. (See Figure 1.) Cell sites have createdunwanted interactions between transmission towers and communi-

Layton “Mayor Vows...”

Layton “D.C. Official...”

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ties that are said to be increasing as wireless becomes more popular.According to a Fish and Wildlife Service (FWS) expert concernedabout the effect of the towers on migratory birds, 45,000 towers existthat are over 60 meters high, and this number is expected to doublein the next ten years. The dependency of wireless on fixed facilitieswas underscored in the World Trade Center attack. Mobile cell towerswere imported into the area in order to expand wireless capacity.

Redundancy and Alternative Choices

Redundancy in design and construction is generally consideredindispensable and invaluable for structural integrity and soundness and,as such, has been a basic and traditional feature of engineered systems.*

In their famous work on accidental structural failure, Levy andSalvadori underscore the critical importance of the concept of redun-dancy: “In practice, all structural failures may be considered to be dueto a lack of redundancy” (55). Specifically, they point out that theadvantage of structural redundancy is that “It allows the loads to becarried in more than one way, i.e., through more than one path throughthe structure” (56). From the perspective of infrastructure planning,redundancies among infrastructure types provide functional flexibil-

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FIGURE 1Selected Trends in Wireless Subscriptions and Cell Sites

“Curbing Tower Kill”

Guernsey

*Although redundancy is generallyimportant, there are instanceswhere it can produce a drain uponresources and increaseinterdependencies to a point whereit creates the very vulnerabilities itis trying to prevent.

Source: Graphed from Cellular Telecommunications and Internet Association

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ity and trade-offs among and between infrastructure systems.Easterling points out, for example, that redundant transportationroutes between rail, highways, and air routes have afforded theopportunity for specialization as well as intermodal switching forpassengers and providers.

The events in lower Manhattan on September 11, 2001 under-scores the role of redundancy and its subtleties in the ability of a regionto restore its infrastructure. Although initially, power, information andcommunication, water, and wastewater infrastructures covering arelatively large area of lower Manhattan were massively disrupted,initial recovery was relatively rapid given the extent of the damage.This occurred because of the ability of operators to decouple, disen-gage, and reroute the systems within and around the damaged area.Redundancy initially built into the system to substitute for or bypassthe original interdependencies created needed capacity. The successof the overall recovery effort depended on the ability to build newnetworks and reroute networks to new power centers. For example,new mobile cell towers were brought in by wireless facilities toexpand wireless capacity. The success of the Internet apparently wasdue to redundancy in the lines—the ability to link high-speed accesslines from many different directions.

Failures, however, in some of these systems are attributed to thefact that redundancies may have only been apparent. “Some of thosemultiple lines travel the same conduits to the same routing centers,”and the conduits or routing centers were not redundant enough towithstand the damages.

If many system components are redundant, but a critical link isnot, then overall system redundancy and its ability to withstand asystem failure can be compromised. This was underscored in thepower outage at Newark International Airport and other parts ofnortheastern New Jersey on June 20, 1997. According to Wald,although power production, transmission, and distribution componentswere typically highly redundant, substations, such as the one at PublicService Electric & Gas Company’s Bayway Switching Station wheretwo networks interconnected, were not redundant. Thus, transformerfailures within the substation that served all of the airport feederscaused a system-wide failure. Recent developments in switchingtechnology using power chip processors may address this limitingfactor in the ability of electrical systems to meet greater and more variabledemand, with electric power coming from further and further away.

Redundancy is often reduced as a result of weighing the in-creased costs of construction to provide for redundancy against thebenefits of added protection given the probability of failure. As

GuernseyYoung and Solomon

Guernsey

Wald

Fairley

Organization Space

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failures become more frequent and extreme events become the normor the consequences more severe, this calculus becomes less convinc-ing. When redundancy is reduced or limited, not only are structuresvulnerable but, needless to say, the social systems that depend on themare also at risk. Non-redundancy has led to a number of infrastructurefailures (and the potential for others) that are relatively few in number,but when they have occurred, their social impacts were quite cata-strophic. Two examples in the areas of transportation (bridge con-struction) and water supply (transmission and distribution) serve toillustrate the importance of redundancy in infrastructure systems thatare highly interdependent with their natural and social environments.

Bridges: Redundancy for User Safety and ReliabilityIn 1983, a section of the Mianus Bridge along I-95 in Connecticutdropped out because of the rusting of a single pin from waterinundation, and the accident resulted in several deaths. This was sucha dramatic occurrence that it led to the National Bridge InspectionProgram in the United States and a serious examination of bridgesnationwide with similar designs. A key contributing factor to thecollapse was considered to be non-redundant pin and hangar assem-bly construction. The roadway was held together by four pins, and thefailure of any one of the pins could cause a collapse. The absence ofredundancy allowed a sequence of other factors—human, environ-mental, managerial, and physical—to contribute to the problem. Thewearing away of the pin was the result of water inundation. Watercame in contact with the pins because of inadequate drainage alongthe bridge’s surface. The drainage problem was a consequence of adecision to pave over the drainage ditches during a resurfacingoperation to save money, which then allowed water to drain over thesides of the bridge, thereby coming in contact with the pins below theroad surface. The pins were not painted regularly enough to resistrusting. Finally, the inspection process was not carried out in a waythat would detect conditions under the bridge (pins were below theroad surface). Although any one of these conditions had a very lowprobability of occurring, any single condition occurring made theadverse consequences of the other conditions much more likely.Moreover, there was no single management system in place withresponsibility and oversight cutting across all of the functional areasfrom design through operations and maintenance over which theseconditions were spread out. The fact that these problems occurredover a very long period of time also exacerbated the ability of anintegrative management system to address the problems.

National Transportation Safety BoardZimmerman, “Planning andAdministration”

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Alternative choices could have been made at any point to reducethe contribution of any one of these factors to the collapse of the bridgeif the relationship among the system components and operations(drainage, painting, subsurface inspection, etc.) had been known.Alternatives could have been any one of the following actions:keeping the pins painted so they would be free of rust, increasing thenumber of structures holding the roadbed intact to increase redun-dancy, maintaining the drainage ditches properly to prevent waterinundation in the substructures, and finally, having an inspectionprocedure that would have detected the problem. Because none ofthese was used and because responsibilities for employing thesealternatives were spread across many organizations, a domino effectoccurred that ultimately led to a catastrophe with three deaths andtraffic disruptions that lasted many months over a transportationcorridor that carried close to 100,000 vehicles a day.

Water Supply Systems: Redundancy in Service DistributionThere are 3,575 km of aqueducts in the United States, and many timesthat number of distribution lines that extend from them, that arevulnerable to earthquakes. According to figures compiled by Hermanet al., the total number of distribution lines for about a dozen of thelargest cities is many thousands of miles within the official boundariesof those cities alone. The need to meet the growing demand for watersupplies further from population centers inevitably increases theextent of these water distribution lines.

Certain configurations of water supply distribution lines thatrely upon redundancy introduce greater flexibility than others. Denseurban areas can afford to, and are almost forced to, adopt a matrixstructure for their water distribution systems because of the densityand the street networks. The New York City system is an illustrativecase. The New York City water distribution system, for example,consists of 6,000 miles of water mains that carry about 1.6 billiongallons per day (b/g/d) over an area of 308.9 square miles. Thisamounts to a density of 19.4 miles of water main per square mile. NewYork City is, as one would expect, at the higher end of water linedensity among cities in the United States. The density of water lines,however, shows surprisingly little variation, in general, with thedensity of cities, ranging from about 16-20 miles of water distributionlines per square mile, while population per square mile varies fromabout 3,000 (Atlanta) to 23,000 (New York). This seems to suggestthat to the extent that density implies redundancy, such cities maypromote the flexibility that redundancy offers.

New York City’s breakage rate for water pipes is about 500 to600 breaks per year, but a report by the Comptroller’s office indicates

Scawthorn et al. 1991, 2001

Zimmerman “The New York Area...”

Herman et al.

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that although the absolute rate in breaks per 1,000 miles of line hasincreased since the 1940s, breakages as a percentage of total distri-bution system lines has been declining. The structure of the watermain distribution system contributes substantially to its flexibility inresponding to problems. Because of the density and matrix structureof New York City’s system of water mains, it can easily switch waterfrom one main to another and isolate damaged areas in the event of abreak once the location is discovered, minimizing outages in the shortterm. One needs to recognize, however, that the key, long-termsolution is an ongoing pipe replacement program and conditiondetection system.

In other areas, such as northeastern New Jersey, for example,the distribution system is generally characterized by more linear,branched systems with few interconnections among the branches,which is an outcome of the response of infrastructure to more rapidpopulation growth. In such systems, flexibility is far more limited.Once a section of a main ruptures, outages usually occur and last fordays. In northeastern New Jersey, breakages are fewer in numberthan in New York. However, according to one account of the historyof recent breaks, effects on water supply can be greater because of thelinear (rather than matrix) structure of the water lines. Some ex-amples are noteworthy: breakages occurred in February 1996 (affect-ing 35,000 to 50,000 customers, leaving them without water for threedays), July 11, 1999 (affecting 750,000 customers in Bergen andHudson counties), and May 1, 2001 (affecting an estimated halfmillion people in six counties). In many of these cases, breakagesresulted in poor water service to users in the form of no water, lowpressure, or contaminated water. New Jersey water outages affectedmore people and lasted for more days than New York breakagesbecause of the limited rerouting capabilities of these primarily linear-ized systems.

System Knowledge

Knowledge of infrastructure systems is vital to reducing uncertaintyabout the nature and effects of infrastructure interactions, but at thesame time, knowledge systems can also act as points of vulnerability,depending on how they interact with the infrastructure system.Exclusive dependency upon automated knowledge systems makesinfrastructures vulnerable to errors and gaps in these knowledgesystems. Computer-based knowledge systems can introduce vulner-ability, particularly when they are relied upon to provide knowledgethey may not have been designed or programmed to produce.

NYC, Office of the Controller

HanleySmothers

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Designing and Programming Detection LimitsOur technical ability to detect substances in the environment hasincreased over just the past few decades, and this has had a dramaticeffect on environmental policy and management. This experiencewith chemicals provides an important analogy for infrastructure.Detection is now down to parts per trillion for many chemicals.Computerization aims at expanding that capability in order to avoidcatastrophic failures and accidents. However, limitations in the waysin which we use computers has often done the opposite. Two historicexamples in the area of chemical detection are instructive. One is therunaway reaction that occurred at the Union Carbide facility atInstitute, West Virginia due to the escape of aldicarb oxime, a materialused to produce the pesticide aldicarb. This accident occurred shortlyafter the Bhopal accident at another Union Carbide plant producingaldicarb, where the chemical methyl isocyanate (MIC) had escapeddue to water being inadvertently mixed with it during a washingoperation. After the Bhopal accident, the Institute plant made use ofa computer program to detect gas emissions. The programmingincluded MIC but not aldicarb oxime, so the escape of aldicarb oximewent undetected. The detection of the depletion of the earth’s Ozonelayer similarly went undetected for a long time because the equipmentmeasuring ozone was not programmed to measure low concentra-tions; that is, the equipment was actually programmed to reject lowvalues considered below the error ranges of analytical models(Benedick). It was not until a ground measurement was made, usingconventional technology, that the thinning of the ozone layer wasrealized. In both cases, we can only notice the risks that we measure.

Although these areas differ in substance from infrastructure,they illustrate the centrality of the design of computer-based knowl-edge systems in avoiding adverse effects and, thereby, providelessons for infrastructure. Some examples directly from infrastruc-ture are particularly relevant.

Wastewater Treatment Systems. A spill detection system for waste-water flow was installed in San Diego’s sewage distribution system,designed only to detect very large spills. As a result, it missed a spillthat contaminated Torrey Pines State Beach on July 31, 2001 becausethe spill was below the detection limit.

Telecommunications. Schneider cites a number of examples whereprogramming gaps have been identified as contributing factors tonumerous outages and disruptions of telephone service and high-speed data networks.

Zimmerman “UnderstandingIndustrial...”

Zimmerman “UnderstandingIndustrial...”

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Transportation. The inability of computer programming to anticipateY2K, touched off high-level investments in readiness efforts. Never-theless, in Norway, thirteen high-speed, long-distance trains failed tostart on December 31, 2000 because the computers did not recognizethe date.

Adaptability or Flexibility of Detection TechnologiesSensing systems are pervasive throughout utility infrastructures toimprove system knowledge and control, but they must be specificallydesigned into those systems in a way that is compatible with both thephysical and human systems.

Supervisory Control and Data Acquisition (SCADA), for ex-ample, is one commonly used type of system for the detection ofconditions within distributed networks of pipes. Computer chips thatare imbedded in fixed structures or materials such as concrete areanother example. DNA chips are among the newest additions “im-bedded” in fluid materials, e.g., water, that enable the detection of afar greater number of substances in water supplies. Visual techniquesfor detection are common and include video camera-based tech-niques with magnified imaging to check road conditions. Othertechniques are used for the detection of currents by photographingbubble patterns as a basis for studies of erosion.

The limits of these systems are as important as their capabilities.SCADA systems are subject to interference and not necessarily easilyadapted to changes in the information technologies with which theyinterface to deliver information. Imbedded chips are not easily changedonce they are put in place. In an extensive review of diagnostictechniques for sewer systems that employ closed-circuit television,Makar observed the many advantages and disadvantages of thetechnique as well as others involving radar and lasers, ultimatelyconcluding that the selection of any given detection technology mustbe determined by very specific conditions.

Ultimately, this calls for rethinking the management and trainingof infrastructure managers. The ability of engineers and operators tomanage both the new technologies and the information technologythat supports them has become, in many instances, a limiting factor totheir application. For example, an Australian survey of engineers’knowledge of information technology was found to be even toolimited to effectively understand and develop contracting proceduresfor others to do the work.

The Associated Press

“Engineering Professor...”

Hartman

Institution of Engineers

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Conclusions

Every new generation of technological innovation faces a need toconnect with the technologies of previous generations. What isdifferent now is the rate and degree of change in the availability of newtechnologies and the magnitude of the population actually and poten-tially affected by such changes. Acknowledging systeminterdependencies, employing redundancy to reduce the level of risk,and building a knowledge base that is consistent with the servicesthese systems perform is likely to require an entirely new conceptualframework in spite of the familiarity of the concepts.

We cannot ignore infrastructure interdependencies and the factthat they increase uncertainties in what we can expect from ourtechnology. Redundancy partially addresses these uncertainties. Thematerials used in our infrastructures are often rigid, and we have tomake up for the rigidity of pipes, conduits, tracks, and circuitry byintroducing flexibility in design and service, which often impliesredundancy. The technology of knowledge systems must connectuser and community interests to the systems that serve them.

Constructive approaches to reduce the adverse effects on socialand natural environments that occur from interactions among infra-structure systems have been addressed by engineering, management,and planning in a number of different ways. Many recommendationsand solutions have been offered that range from relatively smallchanges in building and design techniques to larger system changes.These include innovations in construction techniques, system testingand evaluation, new business models, and most significantly, amore pervasive enlargement of the framework we use to viewthese interactions.

Reducing Adverse Interactions through Construction InnovationsTrenchless technologies have emerged as a means of avoiding thestreet disturbances associated with utility line installation. Trenchlesstechnologies are defined as “no-dig” techniques—those that allowdirect physical improvements to underground infrastructure systemsthrough innovative construction methods precluding the need toexcavate. They are an alternative to surface cutting and encompass anumber of different techniques. The use of trenchless technologieshas been growing. Back in the mid-1990s, 40 percent of one type oftechnique—microtunneling—was being done in just one city, Hous-ton. Thomson reviewed the growing extent to which trenchlesstechnology is now used worldwide for utility line installations.

New York University

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Trenchless technologies are considered to have substantialsocial benefits as shown in the calculations by Thomson for the UnitedKingdom and others. The Transportation Research Board (TRB)report by Iseley and Gokhal pointed out that an important socialbenefit of trenchless technology is the reduction in the frequency ofintrusions, since lessening the opening up of streets and pavementscan extend the lifecycle of those structures, reducing the need forreconstruction. The report cites a study showing an increase inpavement life from 10.9 years to 18.5 years in Burlington, Vermont.Other benefits include the lessening of noise, dust, and traffic. Thereare some historic precedents for the social benefits of these tech-niques. For example, in New York City, the construction of CityTunnel #1, according to historic accounts, was not apparent to thepopulation since the six-year construction partially relied upon verti-cal shafts located away from the streets (113).

Some of the disadvantages are technical and some are social.Technical disadvantages largely relate to site conditions that don’teasily lend themselves to drilling of shafts because of water intrusion,obstructions (including the presence of other utility lines), and landsubsidence or settling problems, thereby potentially increasing costand disruption. Also, maintenance of underground lines could bemore difficult and expensive given the greater difficulty of accessonce they are in place. Social issues that have been identified are thatshafts have to go somewhere, and locations for construction facilitieshave to be selected carefully to avoid neighborhood disruption.

Building a Knowledge Base to Evaluate Interconnected NetworksSystem evaluation can anticipate adverse interactions to avoid thesurprises that occur when different infrastructure systems are com-bined. The “Trust in Cyberspace” report from the National ResearchCouncil observed with respect to information infrastructure that“subsystems spanning distributed networks must be integrated andtested despite their limited visibility and limited control over theiroperation. Yet the trend has been for researchers to turn their attentionaway from such integration and testing questions . . .” (6). There aretrade-offs between a reliance on testing vs. modeling for systemevaluation. With respect to modeling, Hauer and Dagle imply that asmissing information increases as a result of budget cutbacks andincreased size and complexity of machinery, greater reliance is placedon modeling. In many industries, relying on modeling for systemadjustment is considered a major source of system failure. However,the complexity that occurs as a result of the dramatic increase in thenumber of combinations of outcomes that are possible with interac-

Iseley and Gokhale

Tighe et al.

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tive systems may defy any reasonable ability to conduct directtesting.* Yet, the need is clearly there to evaluate complex systems insome way before they are put into full-scale operation.

New Ways of Defining Systems for Public Decision Making andManagementWater distribution line failures demonstrate the need for enlarging themanagement framework from that of a single operating agency withsole responsibility for the condition of the lines to a system of agenciesand institutions sharing that responsibility. This new frameworkmakes possible an array of new solutions to problems. Many of thesenewer potential solutions would target user and impacted populations.

Take the instance of the failure of a water distribution line in adense urban area. Its immediate technical causes might be freeze-thaw cycles (exacerbated by surrounding water), external chemicalcorrosion, load stresses created by heavy vehicles, electrical currentsfrom utility lines and subway trains, vibration, undermining of bed-ding material from improper construction, pressure changes, internalcorrosion, and leakage. If one looks more broadly at these immediatecauses, many players other than the immediate agency responsible formaintaining the water lines, such as transportation agencies andutilities, should assume some responsibility. These entities often endup experiencing the adverse effects of the breakages as well ascontributing to their causes. In large cities with old transit systems,transit agencies often spend large amounts on pumps to remove waterfrom the tunnels, some of which comes from water main leakages andbreaks. Potential contributing factors to breakages are vibration andelectric currents from trains located near the water lines. Thus, if theconceptualization of water main breakages is enlarged beyond con-cern over a water main replacement program to the sources of some ofthe initial causes, a more long-lasting, systems-oriented approach emerges.

New Business Models for Service IntegrationIn the private sector, utilities have been using alternative businessmodels for quite some time to coordinate infrastructure. These rangefrom modest approaches such as agreements among utilities to sharecertain functions, to more extensive mergers and buyouts to consoli-date conflicting activities. Some of these approaches are discussed below.

Shared and Remote-Site Functions. Remote-site meter readings forenergy and water utilities have in some cases been provided bytelephone companies to avoid the expense to those utilities having tohave meter readings performed on-site. CellNet, a telecommunica-

*Testing of complex systems itselfintroduces uncertainty. A number ofindustrial and infrastructure system

failures have occurred during thetesting phase, most notably the

Three Mile Island accident.

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tions firm, uses another technique which imbeds communications mod-ules into electric meters, enabling them to be read from remote locations.

Bundling of Services. Utility “bundling” is a term that refers tomultiple services such as communications, electricity, and waterbeing provided by a single entity. Service coordination is the respon-sibility of the provider, rather than the consumer. There are advantagesand disadvantages to this. Advantages are time savings for both usersand providers in consolidated services and taking advantage of theutility most familiar with the operation or owning the particular right-of-way for distribution lines. Disadvantages are that consumers ofinfrastructure services may not want to deal with a single entity for allof their services, preferring to retain their right to select their vendors.Reichman conducted a survey of 1000 residential users, and theresults showed that half preferred buying individual services, andamong affluent college graduate heads of households, 59 percentpreferred retaining individual services.

Mergers and Buyouts. A more formal and extensive means ofcoordinating utilities is for one company to merge with or buy outcompanies in other utility areas. Large private companies, for ex-ample, known for their water supply operations, i.e., Vivendi, SuezLyonnaise des Eaux, and Thames Water Co., have also been enteringtelecommunications and energy businesses for some time. Theseconsolidations may not always cover or integrate these services in agiven geographic area.

Shared Rights-of-Way (ROWs). Associated with the “undergrounding ”of infrastructure and the bundling of services is the use of commonrights-of-way for different utility lines. Although this provides thepotential for spatial coordination of distribution networks, it does notnecessarily coordinate activities to prevent disruption unless allutilities sharing a corridor are held to the same time schedules forinstallation of lines.

In conclusion, tackling the adverse effects of theinterconnectedness of infrastructure systems and turning those inter-dependencies into positive features will require new means of coor-dination, a greater emphasis upon redundancy, and a reliance on newknowledge systems that reflect these goals.

Masud

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Acknowledgment

This paper is based in part on work supported by two grants from theNational Science Foundation: the Institute for Civil InfrastructureSystems (ICIS) Cooperative Agreement No. CMS-9728805 and“Integrated Decision Making for Infrastructure Performance,” GrantNo. 9526057. Any opinions, findings, and conclusions or recommen-dations expressed in this document are those of the author(s) and donot necessarily reflect the views of the National Science Foundation.

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