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NYC 9/11 Public Portal Document

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understanding of residential choice, retail trade location, and transportation demand behavior. This understanding is expressed in economic and behavioral theories, and the theories are implemented for the study of actual situations through the use of computer models. The work reported in this Handbook represents the state of the art with respect to one very important class of theories and models. At the outset, however, we need to take note.of the fact that all of this progress has not solved Haig’s original problem of { putting planning on a fully scientific basis, and hence perhaps on a basis which would turn the making of plans into an automatic process. Optimization theory has grown at the same time as the theory of urban function and urban models. Optimal solutions are now known for many particular urban functions, as we will describe in connection with this work. But the same development has identified a class of intractable problems for which optimal solutions are unlikely in reasonable time, even with the anticipated enormous increase in computational power. The overall problem identified by Haig suffers from exactly this kind of intractability, given the demonstrated need for many urban activities to form multiple clusters for efficiency and amenity. Much study suggests that one of the most important outcomes of fifty years of research is a negative result — a "failure" — for science, which corresponds with a positive result for the art of planning and public policy making. This result tells us that the largest decisions about the structure and function of the region, and the investment of public and private funds in major improvements, have to be taken with careful exploration and forethought, and with detailed attention to their consequences. Computer models and economic or behavioral theory can provide many instruments for tracing these consequences of alternative decisions, but they cannot be expected to reliably produce the broad outlines of acceptable, affordable, and effective plans. The use of extensive surveys, behavioral analysis, and computer models of system performance began in the current period with transportation planning studies in the mid-1940s. These studies spent over a decade in learning what governs user choice in transport systems, and how these choices combine to produce congestion or its absence in the use of facilities. These studies did not produce plans by machine: these were handcrafted as before, but their effectiveness could be studied in greater depth. The work described in this Handbook draws on the experience of that early sequence of ’studies for the work of tracing out paths and costs of travel under alternative assumptions about possible improvements. The same experience uses these costs to calculate the choices which people would make in the future and under changed circumstances between different modes of travel, such as subway,' bus and auto.

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