Maurice Kilbridge, Robert O’ Block, Paul Teplitz

THE ROLE OF MODELS IN URBAN PLANNING

INTRODUCTION

Planning, in its broadest sense, is ordering the relationships
 of means to ends. To plan for our cities in this sense
we would first establish goals, then select from among
alternative policies and programs those means considered
most likely to achieve them. Once ordered in time and
space, such means would constitute a plan. The role of
theory in this process is essential: It explains the causal
relationships of means and goals, thus providing the rationale
 for selection among alternatives.

This is obviously not the world of urban planning as we
know it today: a world in which the means available
Frequently determine the goals chosen, in which grand
decisions can rarely be taken, in which we must play
guessing games on the consequences of policies and programs
 for lack of explanatory theory, and in which little
plans grope incrementally toward elusive goals. Perhaps
in a free and pluralistic society urban planning can never
be otherwise; but unless we take improvement as our
premise and search for order and understanding, we will
never know.
Theory is the key to the search for order, for without it
we cannot predict the consequences of alternative means
and so are unable to systematically influence trends of
growth and change. Current theory explains only a small
fraction of urban phenomena; if the meaning of urban
planning is to be fulfilled, more and better theory must
be generated.

Our working definition of the term model is somewhat
narrow: a set of symbolic representations of relationships.
In this instance, of course, we will be referring to abstracting
 urban phenomena to symbolic form and relating
these in a structural and mathematically operational way
(1).
This paper argues that analytic methods, and particularly
symbolic models, can assist greatly in the development
of theory. We believe that this is the major role of urban
models today. We suggest that their secondary role is to
help policy makers sharpen their judgment through more
explicit statement of the assumptions and consequences of
alternative means, thereby limiting subjectivity in selecton
 from among alternative policies and programs.

We describe the relationship of models to theory in some
detail and show how symbolism can serve to develop and
purify theory. We also discuss powers and limitations of
analytic techniques in urban planning. Later we will explain
 the development and use of urban models, emphasizing
 the value of the process rather than the value of
the product. Finally, we will venture into the prospects
for urban models and offer some suggestions.

THEORY, MODELS AND URBAN PLANNING

One measure of the development of a field of knowledge
is the extent of its structured theoretical base which, we
shall argue, is partially equivalent to saying the extent
to which it employs abstract models for analysis and prediction.
 These abstract models need not be fully mathematical
 in form: they may, for example, be block diagrams
 or such representations as the psychological concepts
 of id, ego and superego. Although the language of
symbolism is not rich enough to allow translation of al 1
propositions into precise notation, it is usually sufficient-Iy
 subtle and varied to express the important elements of
reality when these elements are precisely and logically
formulated. A theory which cannot be abstracted to
symbolic representation is more likely suffering from
imprecision than from the inadequacy of symbolism.

Theory and Symbolism
There are four substantial advantages to symbolic representation
 of a theory; the summation of these advantages
generally outweigh disadvantages associated with oversimplification
 or distortion of reality:

I. Conceptuval clarity - conversion of a theory to
a model, or a set of symbolic representations, forces
precise definition, clearly delineated elements and explicit
 statements about the nature of its relationships.
Ambiguities of words and vaguely specified relationships
cannot be tolerated in a model formulation.
2. Improved comparability with known theories
 - viewed abstractly, theories of quite different
phenomena sometimes can be seen to be structurally equivalent.
 This similarity of form may identify the model as
one of a class of models for which theoretical enrichment
and solution methods already exist. This advantage is

ARCH+ 2 (1969) H.8