Tag Archives: service life

Performance-Based Infrastructure Management: From Theory to Practice

Near the end of August, 1971, my advisor signed the paper certifying that my dissertation on Analysis of Systems of Constructed Facilities was accepted, fulfilling the last remaining requirement for completing my Ph.D. studies in M.I.T.’s Department of Civil and Environmental Engineering.  My thesis had been that decision makers—that is to say, the designers and managers responsible for building, operating, and maintaining highways, dams, houses, and other types of constructed facilities—should have as their goal to provide the facilities’ users with system that exhibit qualities of satisfactory performance throughout a defined service life and in a relatively efficient manner.  The novelty lay in bringing together in an explicit and operational way four ideas that were at the time coming into focus in our society and the literatures of engineering, architecture, economics, and political science: First, the concept of a facility’s “performance” has many dimensions. Second, what performance is “satisfactory” depends on users’ values and choices; in a pluralistic society, there will always be debate. Third, the long service lives of constructed facilities, measured in decades or centuries, mandate explicit consideration of uncertainties and risks that performance may become unsatisfactory; something may have to be done in the future to correct the situation. Finally, the resources used to deliver performance cannot adequately be measured on any one scale of value; efficiency can be judged only in relative terms, by comparing available options.

My approach to enabling decision makers to accommodate these ideas drew on principles from economics, psychology, and mathematics to represent performance in terms of three primary measures: serviceability, the degree to which the facility satisfactorily provides the services that users want; reliability, the probability that service will remain satisfactory throughout the facility’s service life; and maintainability, an indication of the effort that may be required for maintenance and repair to ensure satisfactory service.  Serviceability, reliability, and maintainability are not independent, and each may be increased—in principle—by using more resources.  The decision maker’s problem consists, I asserted, in devising and choosing among available options a design or management strategy that offered the best mix, the optimum performance.

Enactment of the National Environmental Policy Act in 1969 (NEPA) was a tangible demonstration of the emergence of a new way of thinking about constructed facilities, or to use more recently popular terminology, our civil infrastructure or built environment. The law’s timing was fortuitous.  As a young professional with a newly minted degree in hand, I became engaged in a thriving consultancy practice, helping government agencies learn how to make their decisions about our infrastructure in a more open, public forum and taking more directly into account the values that a broadly-based user community may place on such resources as parklands, historic associations, wildlife, and clean air.

The one resource that everyone recognized, of course, was money, and infrastructure decision makers soon realized that they needed more of it than in the past to deliver this enhanced concept of satisfactory performance. Limited budgets and competing demands for public-sector spending—notably in the early 1970s on growing military and health-care programs—meant that tradeoffs had to be made.  Maintenance might be neglected or planned repairs deferred.  Of course, one can argue that this was just the crest of wave that had been swelling for decades, but by the end of the ‘70s, some people were growing alarmed at what they saw as an impending infrastructure crisis.  When America in Ruins: Beyond the Public Works Pork Barrel (Pat Choate and Susan Walter, Council of State Planning Agencies, Washington, 1981) was published, it made headlines in the nation’s leading newspapers, a rare feat for any discussion of constructed facilities (later reprints changed the secondary title to The Decaying Infrastructure).  The book argued that the United States as a nation had been investing too little in its infrastructure and in the wrong places for a long time, and the nation’s economy was now at risk.

There followed a decade of federal government studies and intense debate among economists about just how important infrastructure is as a foundation supporting the economy and just how fragile that foundation might have become.  The debate formed a backdrop for renewed consideration of performance as a useful facilities-management concept, and by the early 1990s I found myself at the National Academy of Sciences, working with a committee of diverse professionals tasked with recommending how best to measure and improve infrastructure performance. We visited several cities, meeting with municipal and state officials and private-sector professional responsible for building and operating a wide range of infrastructure facilities.  The committee’s report, Measuring and Improving Infrastructure Performance, was published in 1996 (Washington, National Academies Press). We observed that practices then current for measuring infrastructure performance were “generally inadequate.” Performance measurement was typically undertaken because the effort was mandated by law or regulatory requirements, or when there was a specific problem to be solved, not because of any broad acceptance that performance measurement is an effective management tool.

More important was the committee’s recommendation that no single measure of performance can adequately represent the varied and complex societal needs that infrastructure is meant to serve. As the report’s summary expressed it, “Performance should be assessed on the basis of multiple measures chosen to reflect community objectives, which may conflict…. The specific measures that communities use to characterize infrastructure performance may often be grouped into three broad categories: effectiveness, reliability, and cost. Each of these categories is itself multidimensional, and the specific measures used will depend on the location and nature of the problem to be solved.”

The committee’s concept of performance had similarities to what I had proposed 20 years earlier.  “Effectiveness” was described as the ability of the system to provide the services the community expects…not so different from what I had defined as “serviceability.”  The term “reliability” was used in essentially the same way in my dissertation and the committee’s report.  What I had earlier considered as “maintainability” is now more understandably referred to as “resilience” and incorporated as an aspect of reliability. Describing “cost”—deriving from multiple resources and distributed throughout a facility’s service life, but definitely dollar-denominated—as a measure of performance was the major difference from my thesis and an important insight.

While historians may claim causal connections between events separated in time and space, such connections are fundamentally uncertain unless supported by explicit testimony from the people involved in later action linking their motivations to the earlier occurrences.  Having myself met twice with Congressional staff to discuss these matters and delivered to them copies of Measuring and Improving Infrastructure Performance and other documents presenting similar perspectives, I would like to imagine that what I and others have learned about infrastructure performance influenced the most recent transportation reauthorization bill Moving Ahead for Progress in the 21st Century (MAP-21, Public Law 112-141, enacted in July 2012) , which features a new federal emphasis on performance measurement. Section 1203 of the act asserts that “Performance management will transform the Federal-aid highway program and provide a means to the most efficient investment of Federal transportation funds by refocusing on national transportation goals, increasing the accountability and transparency of the Federal-aid highway program, and improving project decision making through performance based planning and programming.” (While the U.S. Department of Transportation has for some years issued its biennial Conditions and Performance report to Congress on physical and operating characteristics of the highways, bridges, and transit, MAP-21 is transformative in making an explicit link between performance and national goals.).

The law then states 7 goals that are to be the basis for defining performance, focused primarily on the nation’s highways: (1) safety, reducing traffic fatalities and serious injuries; (2) infrastructure condition, keeping the infrastructure asset system in a state of good repair; (3) congestion reduction; (4) system reliability, improving the system’s operating efficiency; (5) freight movement and economic vitality, improving the national freight network to support trade and economic development; (6) environmental sustainability, enhancing transportation while protecting the natural environment; and (7) reducing project delivery delays, to control costs and promote jobs.  Elsewhere the act makes keeping transit system assets in a “state of good repair” a goal as well.  The law tasks the Federal Highway Administration (FHWA) and Federal Transit Administration (FTA) with identifying specific performance measures to be used to administer the funding programs covered by the legislation, and with setting targets to be used to judge acceptable performance.

The stated goals and performance measures likely to be selected under MAP-21, while not necessarily comprehensive in their coverage, at least address ideas of effectiveness, reliability, and cost.  That it has taken more than 40 years to bring performance-based management into the mainstream one of the principal functional subsystems of the nation’s infrastructure is consistent with the very slow evolution that is a characteristic of civil infrastructure generally.

Infrastructure Service Life as a Matter of Sustainability

The word is everywhere.  People are talking about sustainability, but what does it really mean?  We want sustainable growth, sustainable development, sustainable communities.  In a recent blog posting, the Director of Sustainable Communities at the Natural Resources Defense Council admitted with remarkable candor about the latter topic, “even a lot of environmentalists don’t quite know what to make of the phrase.” 

Most people would probably agree that not using up all available resources needed for life has something to do with what “sustainability” signifies.  Physicists, chemists, and biologists can define with some precision the oxygen, water, and food, required by a group of organisms for a particular period of time, and the quantity of waste products they will produce.  For humans, their communities and their civilizations, there is certainly a lot more to it.  Our population, our history, and our ideas continue to grow, increasing our demands on an expanding range of resources. 

The American Society of Civil Engineers (ASCE) tried to cover everything by defining sustainability as “a set of environmental, economic, and social conditions in which all of society has the capacity and opportunity to maintain and improve its quality of life indefinitely without degrading the quantity, quality, or availability of natural, economic, and social resources.”  Improving quality of life “indefinitely” with no degradation of resources sets the bar quite high.

The Brundtland Commission took a more modest perspective, defining sustainable development as “…development that meets the needs of the present without compromising the ability of future generations to meet their own needs.”  If one considers that our concept of “needs” has evolved over time, along with our technology and other capabilities to meet our needs, then the Brundtland criterion is considerably less stringent than ASCE’s.   As we look to more distant generations, we necessarily have less confidence that their concept of their own needs will be similar to ours.  Although some people will judge it to be technological hubris, we also are inclined to presume that these future generations will find new ways to meet whatever those needs are. 

The idea of discounting the significance of the more distant future is fundamental to the benefit-cost and cost-effectiveness analysis practices.  The practices, developed primarily in the middle decades of the 20th Century, are now widely used to assess the wisdom of decisions involving expending resources to obtain services or other benefits over a period of years.  These capital investment decisions—for example, to build infrastructure facilities—certainly have the capacity to foreclose future options.

A crucial assumption in any such analysis is the discount rate, usually expressed on an annual basis, representing the decline in value of resources that are made available or used at some future time, as compared to their value today.   For a simple example, many people would readily accept the idea that being given $98 today is preferable to the promise of $100 to be received one year hence.  If the proposition is $90 today versus $100 next year, more people may be willing to wait.  These examples represent discount rates of 2% and 10% respectively.  The discount rate used in any particular analysis reflects economic conditions and analyst’s and investors’ expectations about the future.  Higher discount rates imply less confidence and a requirement that the initial investment should more quickly become profitable.  (An interesting footnote: Comparisons of the value of the goods traded by the Dutch to purchase Manhattan from the Native Americans in 1626 to the current assessed value of the real estate suggests an annual increase of 5 to 6%.  It seems unlikely that Peter Minuet could have imagined what would become of the island.)

What can this tell us about understanding sustainability?  If we imagine that life will carry on more or less smoothly for some time, we might apply a low discount rate, perhaps 2% annually, in deciding whether or not to invest in infrastructure.  The discounting calculations would tell us that benefits accruing to a new investment more than 160 years from now would have a present worth less than 5% of their future amount.  If a human generation is about 20 years, we might then conclude that any long-term benefits that will not be realized until the 9th generation after we make the investment and building the facility are not worth much.  If the discount rate is 5%, fewer than 4 generations (perhaps 50 years) are needed.  With a discount rate of 10%, it takes about 30 years to reach the point that returns promised further in the future may not be influential on our decisions today. 

In other words, it may not make much sense to try to think beyond our grandchildren when it comes to sustainability.  Consider this: the initial demonstrations of transistor technology occurred in the mid-1940s, when I was a toddler.  Only a few years earlier, ENIAC I was developed as the first modern computer, using some 17,000 vacuum tubes.  Who then would or could have imagined the microchip and digital computers—not to mention cell phones—my grandchildren today take for granted. 

Perhaps it is only coincidence, but designers of bridge typically assume their structures will last about 50 to 70 years; for highway pavements, the numbers are 30 to 35 years.  Regardless of such assumptions, most of the people responsible for managing the nation’s infrastructure strive to get as many years of service as possible before a facility must be substantially refurbished or replaced.  Only seldom do public-sector owners of infrastructures make provisions at the beginning of the service life to ensure that funds are available to do the right thing at the end.

If we want our infrastructure systems to be sustainable and to serve as a basis for sustainable communities, such a management strategy may be counterproductive.  Long service lives discourage adoption of new technology and responsiveness to changes in users’ demands and society’s values.  Long-lived infrastructures fix the patterns of land development, social and economic activity, and perceptions of spatial relationships on the regions they serve.  Anecdotal evidence suggests we might be better of planning that infrastructures should be replaced, substantially renovated, repurposed, or retired no more than 3 generations after they are initially constructed.  Where rapid changes are occurring in economic conditions (for example, population growth in Phoenix or shrinkage in Detroit) or the technology (electricity generation and control, for example, as compared to municipal waste disposal), the lifetimes should be much shorter.

Seattle’s Alaskan Way Viaduct, for example, an elevated highway constructed to carry traffic past the city’s downtown core, was completed in 1953.  Over the years since it was built, traffic levels and truck sizes and weights had grown to levels that exceeded what the original designers had in mind; the structure was effectively obsolete.  Replacement would have been costly and very disruptive for the region’s highway users and the Viaduct’s neighbors. 

It was the 2001 Nisqually earthquake that moved Seattle finally to declare an end to the structure’s useful life.  The Viaduct was seriously damaged; sections had to be closed for a time. Repairs were made, but much of the public understood that more would need to be done.  It nevertheless took strong political leadership to effect the Viaduct’s replacement—with a tunnel—initiated in 2011.

The now-infamous The Fukushima I Nuclear Power Plant in Japan, first commissioned in 1971, uses “Generation II” technology.  Newer “Generation II” plants have better safety features.  Because nuclear plants are very expensive to build, reducing their allowable service would significantly raise the hurdle for establishing feasibility of a new plant but might also reduce the risk such infrastructures can pose for their neighbors.

There are many more examples that might be given of infrastructures destroyed or removed before the time envisioned by their builders and operators.  Certainly many elements of any particular piece of infrastructure are likely to remain useful beyond the 3- to 5-decade life implied by sustainability considerations.  However, viewing these elements as evidence of overinvestment and designing to ensure that infrastructures can be salvaged, recycled, or put to other uses would be important steps to improved sustainability.