ARCH+: Zeitschrift für Architektur und Urbanismus: ARCH+ : Studienhefte für architekturbezogene Umweltforschung und -planung

ARCH+ : Studienhefte für architekturbezogene Umweltforschung und -planung (1969, Jg. 2, H. 5-8)

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Persistent identifier:: 1571051867188

Title:: ARCH+: Zeitschrift für Architektur und Urbanismus

Place of publication:: Stuttgart

Regularity of issue:: 1.1968-

Physical location:: Universität Stuttgart, Institut für Grundlagen moderner Architektur und Entwerfen

Shelfmark:: Archiv IGMA

Structure type:: Periodical

Collection:: Periodicals

License:: https://www.deutsche-digitale-bibliothek.de/content/lizenzen/rv-fz/

Collection Object

Persistent identifier:: 1571051867188_1969

Title:: ARCH+ : Studienhefte für architekturbezogene Umweltforschung und -planung

Volume:: 1969, Jg. 2, H. 5-8

Year of publication:: 1969

Language:: german

Structure type:: Volume

Physical location:: Universität Stuttgart, Institut für Grundlagen moderner Architektur und Entwerfen

License:: https://www.deutsche-digitale-bibliothek.de/content/lizenzen/rv-fz/

Collection:: Periodicals

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Title:: Heft 8: Semiotik, EDV, Bewertungsverfahren

Structure type:: Issue

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Title:: The Role of Model in Urban Planning

Author:: Kilbridge, Maurice; O'Block, Robert; Teplitz, Paul

Structure type:: Article

Recognizing the merit of these arguments, we emphasize again our contention that the process of modelling, not the model itself, is often the most valuable aspect of this effort. - The planner who is involved in the development of a model can gain new Insight into urban phenomena and relationships. The above arguments present issues to be studied, problems to be met and attacked, not ex- cuses for chaos. This is not to argue that planners should try to model the world. The appropriate role of models in urban planning today is admittedly limited and qualified. But that role is important: - to assist In the development of theory - to provide a laboratory for testing policies and pro- grams - to emphasize evaluation of short-term relationships - to provide predictions and projections Figure 1 is a general schematic representation of the urban planning process. We believe that the greatest potential for models and modeling today lies in the area of theory development and project evaluation, represen- ted by that part of the diaaram within the dotted box. DEVELOPMENT AND USE OF URBAN MODELS While much can be learned from observing a finished model, or by scanning a computer printout of its applica- tion, more can be learned from the discipline of being required to state assumptions and theories explicitly, and by the opportunity to test one’s ideas of urban relation- ships while groping for the model’s parameters and form. The recurring theme of this section will be the value of the modeling process; we will carry it through our dis- cussion of model development, validation, and appraisal, and use it as the essential principle in our argument for the involvement of certain people in the effort . Model Development In an earlier paper (5) we described the four elements central to the development of a model: - model subject - what is the model about? - model function - what is the model to do? - model theory - on what theory is the model based? model method - how does the model use its theory? Defining these elements in response to the above questions is the first step of a modeling effort. Roughly speaking, the subject of the model is that entity or activity which is projected, allocated, or manipulated by the model. There are four essential classes of subject matter in current urban models: land use (6), transportation (7), population (8) and economic activity (9). The function of an urban planning model is usu- ally to project or allocate the subject, or to derive new subjects from it; most models perform two or more func- tions in varying combinations. The theory underlying the model is that set of relationships - stated or implied assumed to prevail between the model subject and the larger environment. Distinguished on this basis, models generally can be sorted into two classes: micro-analytic behavior or "choice" models, and macro-analytic growth-forces or "index" models. The operational method of the model is the mathematical or symbolic form used to carry out the projection, allocation, or 35 derivation. To these thought, and without repeating the content of the earlier paper, we would add some general observa- tions on the availability of data and on the number of factors or variables included in the model. Clearly, the purpose for which the model is being developed is basic to decisions about data and factors included. If the model is to be a generalized or research effort designed for the examination of relationships between urban phenomena, or to state a general theory in symbolic and manipulative form, its essential purpose is to increase knowledge and insight about fhe processes studied. For such models hypothetical or generalized data can be used, and the number of factors or variables can be limited by assump- tions. On the other hand, if the model is to be applied in an ongoing planning effort, accuracy in depicting the real world is desirable. A specific set of data generally must be used, and simplifying assumptions cannot be easily made. Although an applied or practical model is usually devel- oped for a particular city and used only in its planning activities, the time has probably come when we should try to generalize these models by extending them to other cities. If these models do not seem to "fit" when tested in other, similar cities, their validity - even for the city for which they were built - may be challenged. It would seem that data from one city should apply to other cities, at least within certain class categories. For instance, differences in natural setting such as topology, climate, spatial distribution, and so forth, should not affect func- tional data. Moreover, we should be able to rely on the stability of large numbers: the social and economic be- havior of large groups are relatively invariant and pre- dictable. (This is fortunate indeed, since the physical construction that planners undertake based on this behav- ior is quite durable.) In the development of applied models the data available Frequently determines the nature of the model and this is sometimes detrimental to the effort. In a practical situa- ton, with time and money constraints, most analysts be- gin by surveying the available data. They then attempt to shape the model to make the best use of these data and avoid as much as possible the expense of gathering new data. This approach can severely restrict the choice of theory and method employed in the model. For example, if a model depicting market behavior were planned and a look at the data showed that information about market suppliers would have to be specially gathered, the analyst might well reconsider his approach and select a gravity model instead. This is understandable; little is to be gained by developing a model meant for practical applica- tion, for which there is no data. The level of aggregation of the subject matter also will depend to some extent on the availability of data: If the necessary data are available on municipal divisions only, the analyst is well advised to structure the model on this basis and not on census tracts - unless, of course, he is orepared to generate his own census tract data. The seriality of data may also determine the form of model used for if the analyst can obtain data for only one point in time - and few areas have data for more than two or three points - he may be forced to develop an equilibrium modeF rather than a time-series or growth-forces model. ARCH+ 2 (1969) H.8

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