Design lifetime.

The period of time, assumed as a basis for making feasibility studies and design decisions, during which a facility of element is anticipated to provide service; for infrastructures, typically 15 to 50 years. Not necessarily the same as service life or economic life.

Dimension (of effectiveness).

A single aspect of effectiveness that can be discussed and assessed with minimal reference to other aspects (e.g., traffic congestion on a highway versus the stormwater runoff from that highway)—in principle, linked directly to goal or task set for infrastructure.

Disbenefit.

A negative benefit; an adverse impact or consequence.


Economic life.

The period of time over which infrastructure is expected to repay its full cost. Often determined by financial factors as well as technical.

Effectiveness.

A multidimensional component of performance; the degree to which infrastructure accomplishes the tasks set for it by its owners, users, neighbors, and society-at-large.

Evaluation.

Assessment in which tradeoffs may be made among disparate and generally incommensurable measures, especially for determining preference among several complex alternative courses of action.


Indicator.

A measure, but often not very specific in its information about effectiveness; for example, the color red is frequently used as an indicator of high temperature, which is in turn a measure of heat energy or risk of burning.

Infrastructure.

Not specifically defined in this study; generally used in this report to refer to facilities and their operations and the operating and management institutions that provide water, remove waste, facilitate movement of people and goods, and otherwise serve and support other economic and social activity or protect and enhance environmental quality. Refer to cited references for further discussion (e.g., NRC, 1987; NCPWI, 1988; NRC, 1993).

Level of service.

A measure of effectiveness; frequently used for transportation infrastructure and most well developed for highway and street traffic capacity analysis (e.g., see TRB, 1985).


Measure, measure of effectiveness.

A sign, symbol, or statistic (typically numerical) that people understand to convey information about how well infrastructure is accomplishing its tasks, typically for a single dimension of effectiveness; may be based on some generally used scale (e.g., water or traffic volumes) or defined relative to a benchmark (e.g., observed throughput as a fraction of theoretical maximum throughput) or standard (e.g., observed pollution concentration as a fraction of the level allowable under law). A specific indicator.

Measurement.

Structured observation and documentation of one or more aspects of the behavior or characteristics of a system. Implies no assessment or evaluation.



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