At the end of the study, the committee finds that many unanswered questions remain as obstacles to performance measurement. There is work to be done by practitioners and researchers working together to improve methods for dealing with multi-objectives, performance measures, and stakeholders in a decision process. Better ways are needed for accounting for uncertainty and for multimodal infrastructure management. Data collection and management underlies virtually all aspects of performance measurement, and here too, improvements are needed.

HELPING DECISION MAKERS

The point of performance measurement is to help decision makers. For infrastructure, these decision makers include not only the engineers, architects, urban planners, public administrators, elected officials, and other professionals who develop and operate infrastructure but all the citizens, residents, and neighbors who own the infrastructure and occupy the areas that infrastructure serves. In seeking to describe and measure infrastructure performance, one is attempting to judge how well infrastructure is accomplishing the tasks set for the system or its parts by the society that builds, operates, uses, or is neighbor to that infrastructure.

As the committee has defined it, infrastructure that reliably meets or exceeds community expectations, at an acceptably low cost, is performing well. The committee recommends then that performance be measured in terms of its effectiveness, reliability, and cost. Measuring performance presents challenges of multiple expectations that the community holds for its infrastructure, the diverse views on whether those expectations are being met, costs that are distributed over time and paid from several sources, and the likelihood that community expectations and priorities may change during the typically long service life of infrastructure facilities. The specific performance measures used should be meaningful and appropriate to the needs of the decision makers, adequate and comprehensive to support thorough assessment, and have reasonable costs of measurement.

Performance is not the same as engineering ''need" or the economist's concept of "demand," but rather represents an intersection of demand and supply, need, and capability, that can be established only within the context of community interests and priorities. Infrastructure may have other benefits or adverse impacts that are not aspects of its assessed performance, as when urban highways have been said to divide neighborhoods and destroy the sense of community needed to sustain older residential areas. However, such impacts may change community expectations and introduce new factors into the performance measurement.

Judging how well infrastructure is performing typically occurs in a public setting. Many people are likely to be involved, and reaching con-



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