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Critical Unresolved Problems of Urban PlanningAnalysisMelville C. BranchPublished online: 26 Nov 2007.

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Critical Unresolved Problems of Urban Planning Analysis Melville C. Branch

Sound city planning requires a valid theoretical and analytical base. But our present knowledge of the functioning of urban organisms and their analysis for planning purposes does not justify the operational pretensions of city planning practi- tioners, nor the academic claim that city planning is as yet an intellectual discipline and prospective science. In the United States, development of the foundation of fundamental knowledge for sound city planning has been subordinated to strengthening the superstructure of professional practice.

Emulating the paper “Mathematical Problems” presented by David Hilbert at the turn of the century, twenty-three critical unresolved problems of urban planning analysis are identified and explained briefly. City planners are aware of most of these problems separately, but the importance of their resolution warrants collective statement. When these problems are resolved, urban planning will be established as a foremost field of knowledge de- serving universal application.

“Who of us would not be glad to lift the veil behind which the future lies hidden; to cast a glance at the next advances of our science and at the secrets of its development during future centuries? What particular goals will there be toward which the leading [urban planninglspirits of coming generations will strive? What new methods and facts in the wide and rich field of [urban planning] thought will the new centuries disclose?

“History teaches the continuity of the development of science. We know that every age has its own problems, which the following age either solves or casts aside as profitless and replaces by new ones. If we would obtain the idea of the profitable develop- ment of [urban planning] in the immediate future, we must look over the problems which the science of to-day sets and whose solution we expect from the future. To such a review of problems the present day, lying at the . . . [bicentennial of the United States], seems to me well adapted.”’

These are the words of the renowned mathema- tician David Hilbert addressing the Second Interna- tional Congress of Mathematics at Paris in the summer of 1900, except that references to the field of mathematics have been replaced by the field of urban planning and the occasion changed from the turn of the century to the bicentennial of the United States. In his paper Prof. Hilbert “presented and discussed 23 individual problems, the solution of which, he was confident, would contribute greatly to the advance of mathematics in the coming century.”’

To advance the theory and practice of city planning during the next century will require much greater

Dr. Branch, AIP, is professor of planning at the School of Urban and Regional Planning, University of Southern California. For seven years he was corporate associate for planning (west coast) and member of the senior staff of TRW Inc., and for nine years a Los Angeles city planning commissioner. He has written extensively on many aspects of planning. -

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knowledge of the anatomy and functioning of urban organisms. For a new era has begun after a

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long history of dealing primarily with the physical form of cities. The scope of city planning now in- cludes ,economic, social, political, legal, technological, cultural, es- thetic, and other major elements of

a city. And in the United States and comparable societies urban planning is conducted through the democratic political process. The vastly increased difficulties of analytical comprehension brought about by this broadened scope of urban planning and its realization by democratic methods are more keenly recognized by urban planners than the many other professions and fields of knowledge concerned with urban management.

From a relatively simple field of knowledge and practice covering a few physical features of the city, urban planning has expanded to become one of the most ambitious analytical endeavors undertaken by man. No other field aspires to the range of con- sideration and comprehension now believed necessary for successful planning at regional, state, and national levels of organization in the United States. Although the urban organism does not have the spatial magnitude of larger governmental entities, it is comparably complex, and analytical comprehensive- ness seems more attainable in urban areas relatively small in size, immediately visible, more real and familiar, and close at hand.

Because of the spread of political power and the increased capability of the disadvantaged to make themselves heard, the focus of urban planning in the United States has recently been on citizen participa- tion, equal opportunity for influence among the different people affected by city planning, and stronger directive controls and means of effectuation. The accent has been on action designed to bring about new legislation and institutional changes relat- ing to city planning. During this period, compre- hensive theory and analysis have been discounted by city planning practitioners, and most of what has been produced by academicians is so abstract or vague that its relevance to real cities is questionable.

Even with broader participation and stronger effectuation city planning will be but modestly advanced, since the analytical knowledge needed to determine how best to apply these operational achievements does not now exist. The multitude of interactions between numerous urban elements are not well enough understood to identify the optimum allocation of available resources among competing demands, nor the points in the functional structure of the urban organism which produce the most beneficial repercussive effects. The meaningful in- corporation of important elements difficult to measure 48

or quantify into an analytical construct of the city remains an intractable problem. Not enough is known about the best balance between minimally regulated market forces and governmental or other interven- tion for certain elements of the city. And at an even more basic level, important concepts and terminology used regularly in urban planning theory and practice are now little more than glittering generalities, in- adequately defined to be included in an analytical construct of the city and insufficiently quantified to be part of a comprehensive mathematical model.

For some time to come i t will probably not be possible to employ in city planning the mass of in- formation available from electronic computers and remote sensing because, as indicated above, the analytical formulation necessary for its use does not now exist. And until such a construct is available, irresistible pressures for more and more information are likely to disrupt and overload the directive system, confound city planners, and force some sort of responsive action even if the information is unreliable and there is insufficient knowledge to apply it beneficially.

Despite these analytical deficiencies, every indica- tion points to the necessity of more and more planning throughout the world whether people want it or not. Modern systems supplying energy, providing transportation and communication, producing prod- ucts and services, or for military purposes require more extensive and knowledgeable planning as they become technically more complex. This means longer lead times to properly plan each of the component operations and projects which make up the system. More planning of many kinds is also needed as the economic, social, and political aims and activities of different countries and groups of people around the world are more closely linked through fast trans- portation, instant communication, trade and services, or the control of disease and pollution. Continued increase in the size and number of metropolises will require much improved city planning for these urban agglomerations to continue to function and provide healthy environments for more and more people concentrated on the land.

Improved city planning requires a sound theoretical and analytical base. Without this base, implicit or explicit as the case may be, an intellectual discipline, substantive field, or science cannot progress. Valid generalizations cannot be made. Experience must be relearned repeatedly. New situations must be ap- proached without proven guidelines. And the body of knowledge comprising the discipline has no con- tinuous structure of coherent logic and analytical conclusion.

Only bits and pieces of a general theory of urban planning exist today. Its development is the most important challenge facing city planners and others concerned with and interested in cities. Regrettably,

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many city planners today believe that theory is not important to their work. Of course they are mistaken in this belief because they are constantly using theory whether they realize it o r not; every thought and act involves o r reflects theory of some sort. City planners cannot hope to understand the dynamic functioning of cities until a reliable theory of comprehensive urban planning analysis is formulated and tested empirically.

Although these problems (displayed in Table 1) are those most critical for urban planning, most of them are equally relevant to other forms and applications of planning.

1. The public interest For years the actions required under the police

power by city planning in the United States have been supported by the phrase that they are necessary and desirable “for the public health, safety, convenience, and welfare.” That there is such a public state o r “interest” has been tacitly accepted for centuries. It is the basis for public health requirements, building and safety codes, and other regulations directed to pro- tecting and improving the condition of municipal inhabitants as a collective entity.

Nonetheless, there is no general definition of the “public interest” which could be adopted as a measure or guide for proposed actions. Those who use the phrase to justify some specific action assume that carrying out the action will automatically add what it provided to the definition of public interest. Thus, the

Table 1. The twenty-three critical unresolved problems of urban planning analysis

1. The public interest 2. Desirable urban market mechanisms 3. Restricting growth 4. City-community size 5. Urban physical form 6. Central city functions 7. Density and circulation in the central city 8. Effects of crowding 9. Density and urban costs

10. Environmental impacts 11. Suppressed effects of urban life 12. Socioeconomic indicators 13. Cost-benefit analysis 14. Risk analysis 15. Forecasting and utilizing new technology 16. Analytical treatment of indefinites 17. Continuity of planning 18. Plan change 19. Citizen participation in urban planning 20. Analytical simulation of the city 21, Analytical core for municipal management 22. Display of information and analysis 23. Evaluating the effectiveness of planning

Hourglass drawing by Richard McCallister, reprinted by permission.

JANUARY 1978

collective public interest is the sum total of all actions with respect to the urban organism which have occurred in its name, whether or not they have been validated in any way. Besides the illogic of creating and defining a condition by adding u p the prescriptions which have been written for it without knowing -

its nature, such a definition would be so lengthy and tortuous an accumulation that it could hardly serve as a practical measure or referent.

In recent years “social indicators” have been pro- posed as statistical measures of the municipal condi- tion or interest. But their expression in numbers does not make them intrinsically more accurate or meaningful if their derivation is imprecise, if their significance is limited because they represent only one aspect of the municipal condition, or because their usefulness depends on interrelationships with other urban elements which cannot be determined reliably.

What is needed is a quantitative or other specific statement of the general, o r public, municipal and urban interest: demonstrably reliable; sufficiently precise to permit comparison over time for a single city and also among different cities; and acceptable as a basis for executive, legislative, and judicial decisions.

2. Desirable urban market mechanisms Societies have always determined the degree of

governmental control of economic market mech- anisms. Historically, this has varied under different economic and social circumstances, and with different political ideologies. In the United States, market mechanisms once dominated by private enterprise have been subjected increasingly to governmental intervention in one form o r another.

Private enterprise contends that the public benefits from “free” markets which are either unregulated or supported by government if this is needed for them to function as business believes is desirable. O n the other hand, governments concerned with the condition of people believe they must establish minimum standards or requirements to preserve and improve the public health, safety, and welfare of the societal unit and ensure its survival.

T h e functioning of both private enterprise and government becomes progressively less efficient as regulation becomes administratively more compli- cated, burdensome, and time consuming requiring a larger and larger bureaucracy. This applies in city planning today to the regulation of subdivisions, construction, municipal utilities, population densities, land use, urban redevelopment, environmental qual- ity, and control or programing of urban growth.

Since a city is most fundamentally an economic organism, it cannot survive without economic viability, much less support municipal planning directed

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toward continued improvement of the physical city and the socioeco- nomic condition of its inhabitants.

There is need for an analytical method of determining what com- bination of freedom for private enterprise and intervention by government in urban market mech- anisms favors: the economic health

of the city at different stages of its development; its functioning in the collective best interest of its inhabitants; and maintenance of as much freedom of choice by the individual and by nongovernmental organizations as is consistent with these objectives.

3. Restricting growth From one viewpoint growth is always determined

by population pressure, new or expanded economic activity, the availability of financing, a desirable environment, or if the initiating force exists, on the lead times required to plan and build new structures. It has been possible for years to limit growth in cities by not extending utilities to serve new structures, by zoning, building codes, health regulations, or some other form of restriction.

What is not yet clear is whether most cities, like most living organisms, inevitably compete with one another. Will a city limiting its growth gradually lose out economically to another community with which it is in competition whether it is aware of it or not-all the more, if to maintain a stable popula- tion or minimum rate of growth, it must expel many inhabitants who constitute the excess of births over deaths which will persist in many American cities for years to come? Urban history suggests that this is the reality.

Consideration of limiting growth also brings to the fore the question whether municipalities are legally responsible for meeting market demand for low- income housing not met by private enterprise, pro- viding these units in sections of the city away from depressed central city areas, and supplying its fair share of regional housing needs. The first two of these responsibilities can be fulfilled by changes in zoning, building code, or new means of financing construction if this is needed-but how to direct where within the community the decentralized low-income units are best located has not yet been analyzed.

The third question concerning regional responsi- bilities is not so readily answered. Will the new low- income housing units be allocated among the cities in the region: proportional to their population, actual or planned; taking into account the percentage of the low-income units in the region provided by the community; following regional or state plans project- ing different city sizes than those existing at the time of the allocation; or according to some other criteria? 50

A rational and equitable answer to these questions will require thoughtful analysis.

4. City-community size

Greek colonies were limited in size by the number of founding settlers. Medieval cities were contained within their defensive walls until new walls enclosing more space were built. The maximum of 30,000 inhabitants for British “new towns” proposed by Ebenezer Howard in 1898 has been increased to a minimum of 150,000 for such communities today. Recently, some cities in the United States have moved to limit or prevent growth.

Engineers seek to establish at what size unit costs of municipal utility systems increase so rapidly that a separate system is more cost effective than enlarging the existing one. This has been difficult to do because so many variables are involved and data are scarce with which to compare the costs of utility systems providing different levels of service at different times and under different circumstances.

Calculating optimum city size is many times more difficult when the full range of systems involved are considered: social, educational, health, protective, and other facilities and services besides utilities; land use patterns; population growth and density; building coverage on the land; transportation systems; environ- mental quality and amenity; even the psychological effects of the physical city on its inhabitants. Optimum city size also varies with different nations, their policies, plans, and stage of development, different cultures and technologies, the economic base of the city, its site, location with respect to nearby cities and metropolitan areas, and the level of utilities and services provided.

Can cost-benefit analysis measure-reliably, sepa- rately and in combination - the major considerations involved in determining the optimum city size for existing cities? Would such a calculative base apply also to new towns or physically distinct communities comprising a large metropolitan area? Or are the variables and imponderables so numerous and dif- ferent in nature that they cannot be quantified, calculated, and conclusively integrated? If such an analysis is developed which can cope with all sig- nificant elements involved in optimum city size, rather than a selected few, it will approximate, if not con- stitute, a determinative analytical model for compre- hensive city planning.

5. Urban physical form The spatial form of the built-up area of cities-as

viewed from high above-has always varied with site and situation, different stages in a city’s development, military defense, means of transportation, population growth, or other factors, events, and decisions. The

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prevalent urban form is roughly circular, but other configurations exist, are adopted or recommended for new towns, or are proposed as long-range spatial objectives for existing cities: square, rectangular, star-shaped, linear, figure-eight, irregular, mega- structure. Associated with each of these geometric shapes in plan is a related profile of building heights. This vertical dimension is critical in the concept of the megastructure community contained within a single extensive multistoried structure. Each spatial form also displays or implies locations for different land uses within the existing or proposed pattern.

Because the configuration of cities today in tech- nologically advanced countries relates so closely to the spatial arrangement of their primary transporta- tion and utility systems, these networks can be used to shape expansion of an existing city. And they can more easily and readily establish the overall form of at least the first stage of a new town.

A method of analysis is required to ascertain the best overall shape for a new or existing city. It must be understandable and conclusive for decision makers. Many considerations are involved: the nature and efficiency of transportation, utility, and service systems; disposition of different land uses; density of population and building coverage on the land; loca- tion and size of open spaces; air quality; micro- climatic conditions; environmental amenity; the inter- face of built-up areas with surrounding countryside; and the capability of the city to expand or contract horizontally and vertically. While quantitative analysis can be made for certain of these considerations and their interactions, others must be resolved by structured logic and judgment.

6. Central city functions Throughout history certain activities are normally

located in the central area of cities. “Downtown” is the focus for transportation routes which have radiated outward from earliest times. As the geometric center of generally circular surrounding urban development, it provides “equal access” to and from all parts of the community. This spatial fact and feature are im- portant for certain urban activities: specialized markets; one-of-a-kind commercial establishments; unusual businesses concentrated downtown to meet customer demand for convenient choice between them; financial and other organizations requiring frequent contact in person; unique institutions serving the general public or a group of people distributed throughout the community. City centers also have historic and symbolic significance because they are usually the site of first settlement, the location of important governmental and religious edifices, and therefore often the cultural heart of the community. Until modern military developments, they were the most protected places in the city, farthest from en-

JANUARY 1978

circling city walls or other pe- ripheral defenses.

Some functions of city centers persist, others change over time. This is especially evident since the advent of the automobile, the pro- liferation of great urban concen- trations, and their spread over large areas. Witness the local super- market, branch bank, library, and government office, movie theater, or department store and corporate headquarters no longer necessarily downtown.

With increased congestion and costs of operation in the central city, determination of what urban activities need now or will need in the future to be centrally located is an important question. For example, technological advancements have improved perform- ance and reduced the costs of computer and video communication, making decentralization a choice for some activities requiring centralization heretofore. And the feasibility and desirability of decentralization relate to the physical form of the city, its land use, spatial distribution of population, location of sub- centers, profile of building heights, and the extent to which transportation systems are focused on down- town.

7. Density and circulation in the central city

Since earliest times, the close correlation between population density, land use, and transportation has been recognized. It has long been known that the more people living or working beside a city street, the more congested and slow-moving the traffic on the street. Engineers can calculate traffic capacities on single thoroughfares which do not have so many interconnections with other streets that the combined conditions affecting traffic on the thoroughfare cannot be expressed mathematically.

Traffic analysis is much more complex for an entire downtown district. These areas are usually composed of several hundred or more small city blocks, with adjoining streets so closely interconnected that traffic conditions on every street affect vehicular flow on every other street and at every intersection. There are many hundreds of separate properties with buildings occupied by different numbers of people coming and going by different means of transporta- tion, mostly during peak hours of daily travel. Goods of different kinds and quantities are shipped and received at each of these properties at various times of day. A system of traffic controls and public trans- portation restricts movement on surface streets. And the entire downtown complex is linked at its periphery by connections to the citywide transportation net- work which limit the flow of vehicular traffic in and out of downtown.

So many variables are involved that the relation- 51

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ship between population density on each property and uncongested movement of traffic on the down- town street system cannot be cal- culated today, although preserving a balance between the two is a critical requirement of sound city planning. Until a method of analysis is developed to support more

rational decisions, individual pressures to over- build in the central city will persist until intolerable congestion forces a halt, enormous expenditures are required to alleviate traffic conditions which could have been avoided in the first place, and a new cycle of overbuilding and consequent congestion is begun.

The analysis will be successful when it permits calculation of the effects of a proposed new structure on a desired level of traffic movement throughout the downtown area and identifies any changes in the transportation system necessary to allow construction of the building and preservation of the desired traffic flow.

8. Effects of crowding Because concentration of people is characteristic

of cities, the benefits and costs of different popula- tion densities are part of basic urban research. And although the crowding of people in modern cities is less than was common in Europe in medieval times, it is high enough in parts of many cities, and there are enough proposals favoring higher population densities in the future to warrant thorough investiga- tion.

There are unanswered questions concerning widely accepted suppositions relating to increasing popula- tion densities. Are social contacts indeed more numerous, stimulating, and beneficial? Are mutual cooperation and personal security more or less? Are monetary costs for the individual, family, and municipality more or less “all things considered”? Are there effects of crowding on health or other aspects of the human condition disassociated from income and educational levels?

Experiments with animals other than man show progressive abnormalities with overcrowding. Cogni- tive mapping suggests that the physical environment affects man in subtle ways unrecognized by him. These results relate to the well-established psychological fact that people are subject to internalized or uncon- scious mental-emotional forces brought about by the environment, of which they are totally unaware. This suppression from conscious awareness is the means of protecting a person from the consequences of condi- tions or events too disruptive or painful to be borne in mind continually.

It would be most helpful if these and other questions relating to overcrowding could be answered defini- 52

tively and unequivocally since they relate so directly to desirable densities of population-one of the most fundamental and important considerations in city planning.

9. Density and urban costs Studies have been made suggesting that unit costs

of necessary public utilities are less in high-density urban districts than in the low-density suburbs of the city. Some people conclude from this that urban efficiency and environmental amenity are improved by concentrating many dwelling units in small areas, rather than spreading them out at much lower average densities.

The problem with this conclusion is that there is much more to the question of desirable density than the provision of water, storm drainage, sewerage, and energy. Are the unit costs of other critical and important services-such as the protection of persons and property, public transportation, education, health, social programs, recreation, or municipal administra- tion-also lower when densities are higher?

Whether dense urban living is desirable during the many years before its reduction is feasible depends on the balance of many costs and benefits besides those considered in present studies. Are dense physi- cal environments generally healthful or strainful? Does close proximity in daily living promote social ac- commodation and cooperation between neighbors, or does it increase tensions, antagonisms, conflict, and crime? Do noise and other environmental pollutants in- crease with density? Are sanitary conditions more diffi- cult to maintain? Is physical deterioration more rapid and are maintenance and replacement more costly in densely built-up areas? Are private and public investment, unit construction, and operating costs higher? Is travelling to and from work cheaper and less time consuming in the aggregate, with unit production costs constant? Is dense development more or less esthetically pleasurable than more open environment? Do people have a definite preference for one of the two? How does this vary with age, family size and composition, income and educational levels, property taxes, or social situation?

Certainly it would be most important for city planning if all significant considerations could be incorporated in some form of cost-benefit analysis which would permit conclusive comparison of density of urban developments, costs, and human needs and desires in an inclusive and meaningful use of the term. Every aspect of cities relates in one way or another to the number and distribution of people and struc- tures on the land.

10. Environmental impacts Environmental impact reports (EIRs) have added

a new dimension to city planning by forcing formal AIP JOURNAL

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consideration of the environmental effects of pro- posed urban projects on the immediate neighborhood and the city at large. They are a means of controlling environmental pollution, properly locating proposed activities, and making their realization contingent upon conditions or requirements which would mini- mize harmful effects upon the urban environment.

Unfortunately, EIRs were frequently misused when first applied. Planners pretended to themselves and to others that all or most environmental impacts could be analyzed separately and collectively with conclusive precision. EIRs have been used at times by both proponents and opponents to delay or pre- vent project approval rather than for genuine evaluation. Environmental effects are often treated as political issues or symbols of the moment rather than as conditions vital for society and its future.

There are methods for measuring separately most of the physical impacts and some of the socioeconomic effects of a proposed project, but there is no definitive way of calculating their relative importance and collec- tive impact on the millions of interactions which constitute the enormously complex content of the urban environment and comprehensive city planning.

What is needed now is an analytical method of identifying the three or four most important adverse impacts of a proposed project, and the same number of most significant positive effects. To the extent possible, scientific measurements and calculations should be employed, butjudgmental and other means of subjective evaluation should be incorporated when these are the only, or best, way of arriving at certain conclusions. The analysis will probably require improvement in the present processes of formulating individual and group judgments. It should be suf- ficiently clear and compelling to withstand refutation by decision makers because of some manifest analytical weakness.

11. Suppressed effects of urban life Psychology has established three levels of human

awareness: conscious, preconscious, and unconscious. The first includes those conditions and experiences of which we are immediately and continually aware. The second involves thoughts and memories which have been pushed back into partial forgetfulness for some reason and require deliberate effort to recall. The third level consists of the unconscious mind and emotions containing material about which the in- dividual is completely unaware: emotional drives from the primitive past which have been superseded but not erased by the conventions and restrictions im- posed by civilization; and thoughts, feelings, and oc- currences too emotionally painful or physically disruptive to recall continually.

The unconscious mind and emotions have been largely disregarded in determining environmental JANUARY 1978

impacts and planning cities because conclusive evidence concerning their effects is lacking. Yet it is known from medical experiments with animals, including humans, that frequently repeated loud noise causes physiological damage, psy- chological strain, and disability on occasion. But many people suppress these effects and believe they are not disturbed. Experi- ments producing aberrant behavior in animals when they are crowded in confined space are suggestive but inconclusive with respect to man.

Besides possible pathological consequences, medical evidence strongly suggests that even the tensions of ordinary life affect urban inhabitants adversely in ways they do not realize. But there is insufficient scientific proof to convince skeptics and the body politic to support city planning policies directed specifically to reduce the unconscious tensions of ordinary urban existence which result from traffic congestion, fear of crime, the bureaucratic maze, anomie, or even the unrecognized insecurity created by the complete dependence of the city dweller on other people providing specialized services for almost every requirement of living and survival.

Experiments need to be developed which will establish beyond a reasonable doubt the significance of the unconscious effects of the urban environment on its inhabitants, and measurements devised to indicate the severity of these effects. This will complete the scan of environmental consideration in urban planning: affecting population densities, transporta- tion, health care, recreation, and other municipal activities in various ways.

12. Socioeconomic indicators The physical components of a city can be counted

or measured and their condition evaluated by visual examination, engineering test, scientific analysis, or aerial remote sensing. The data provided by such methods are accurate enough to support conclusions and actions relating to the quantity and condition of many physical elements and aspects of city planning.

But the socioeconomic state of the city which generates its physical state and most directly represents the condition and contentment of its population is more difficult to determine. The economic status of people is the best known, mainly through income data. But these data do not take into account such factors affecting real income as consumer debt, other obligations, and unreported earnings. Also, income data are statistically less reliable than generally presumed, particularly with respect to minority groups and the disadvantaged for whom such in- dicators are most needed.

Living conditions are not easily evaluated. The size 53

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of the dwelling unit and working space are only partly indicative of their livability and acceptability. Their quality is not determined by sanitary facilities, utility services, and maintenance level alone. What is substandard for one family or per- son may not be for another group or culture. Health statistics illumi-

nate only one important aspect of the quality of life. Personal contentment with living conditions and

satisfying relationships with other people are probably the most important indicators of the socioeconomic situation ofeach person, but they are the most difficult to measure individually and collectively. Opinion surveys not only are too expensive for regular use, but even with elaborately structured interviews cannot completely determine attitudes.

Reliable and practical methods of measuring socio- economic conditions and attitudes would permit these elements of a city to be monitored more scientifically and accurately over time, and different communities to be compared. Such data would provide a basis for evaluating the socioeconomic effects of policies and plans. They would probably also disclose increasing social tensions and possibly anticipate potential disturbances.

13. Cost-benefit analysis Throughout history people have constantly con-

sidered the pros and cons of their actions and inten- tions. An accounting system developed as a basis for evaluating commercial activities and making many business decisions. Most recently, largely as a con- sequence of increased environmental awareness and concern, efforts are being made to identify and calculate all of the costs and benefits relating to an existing or proposed urban project or city planning activity.

The great advances in knowledge during the past several centuries have confirmed the interconnection of all things, microscopic and macroscopic. Actually, every project or activity involves an infinity of repercussive effects. Some of these are between elements: such as transportation and land use, or municipal services and public health. Others are responsive within a subsystem, such as automobiles and the demand for fossil fuel, highway accidents, repair services, automobile related insurance, traffic control requirements, air pollution, and employment -to name but a few of the effects of automobiles which reportedly support one of every seven persons employed in the United States.

But cost-benefit analysis is now very limited in its coverage and range of reliable calculation. At present it is analytically impossible to measure the enormous number and diversity of elements and effects we know are involved in every existing and proposed 54

activity so that they can be meaningfully integrated. Many physical entities can be counted and correlated numerically, but other vital considerations cannot be assessed in the same way: esthetics, good will, political impact, precedential effects, cultural sig- nificance. Furthermore, complete analytical coverage would be far beyond the budgets of municipal planning agencies.

An analytical construct is needed which can be used to quantify and integrate diverse costs and benefits in a manner which is scientifically, mathematically, and empirically valid. Since all related costs and benefits cannot now and probably never can be com- prehended and correlated completely-nor com- pletely covered in practice-a method of determining those that are the most significant must be found. Attainment of these analytical advances would support a simulative model for comprehensive city planning.

14. Risk analysis Risk analysis is particularly important when fear

or affluence leads many people to believe that society can and should protect them against any and all hazards: crime, insurrection, disease, contamination, accidents, earthquakes, landslides, storms, floods, tidal waves, fire, explosion. Some hazards are accepted voluntarily by individuals, for example when they elect to travel by car or aircraft. They cannot now affect other risks directly, such as those from earth- quakes or hurricanes; but they can reduce the effects of some hazards by choice of community and exactly where one works and resides. Individuals can also take various actions or conduct themselves so as to prevent or reduce the risk or degree of damage to their person and property. But these choices and actions involve costs whether they are taken by the individual or society collectively in the form of building codes, health and safety regulations, or capital works.

The public is unaware of the wide differences in statistical risk from different hazards, their relation to the general death rate from disease, and the cost and consequences of different degrees of reduction in the risk. N o society has the capacity and resources to reduce all hazards to the extent possible. A choice must be made explicitly or implicitly between different risks and the degree of prevention or protection with respect to each.

Urban risk analysis needs to disclose: the relative danger represented for the individual and population by the greatest hazards; the costs of different degrees of reduction in each risk; and the relation of both of these to other elements and considerations of city planning.

Also involved is the extent to which the body politic deliberately determines what levels of respective risk they will accept at what cost, or whether this is

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decided indirectly by people’s actions and economic choices in the market place, and their influence o n legislation reducing the risks from hazards or their destructive impact.

Finally, the physical and budgetary effects of actions and expenditures with respect to risks on other elements of the city must be gauged: on land use, population density, transportation patterns, utility and emergency services, housing costs, taxes.

This analysis and these policy considerations should form the basis for rational decisions in comprehensive city planning relating to urban hazards and risks.

15. Forecasting and utilizing new technology

Techniques of obtaining the collective judgment of a group of experts by a structured process of separate questioning and response are used to forecast when new technologies may be available to general application. The unidentified predictions of every person on the panel are fed back to each participant to see if knowing the opinion of peers alters individual judgments. Cross-impact analysis seeks to determine from the experts the interdependencies between technological developments in different areas of scientific study, and to identify any “critical path” of successive achievements which must be realized for a particular technological advancement to occur. Not enough time has passed as yet to establish the reliability of these techniques by reviewing the accuracy of forecast dates still years in the future.

Modern cities depend on different technologies for their existence and effective functioning. In one way or another, technology determines the type of municipal subsystems: water supply, sewerage, energy supply, communication, transportation, pollution control, and every other physical or socioeconomic subsystem of cities. Forecasting the time when new technologies will be perfected is therefore a matter of great importance.

Clearly there is more to the question of introducing new technologies than forecasting their availability for municipal use. When will it be economically ad- vantageous for the city to replace an existing subsystem with another employing a new technology? Would this new subsystem interact with others in technical ways which affect whether or when it should be undertaken? Would the proposed subsystem affect local employment, social conditions, safety, personal privacy, or some other interrelated socioeconomic consideration? What is the priority of the proposed subsystem compared with other urban needs and necessities? When could it be effected with the source and application of funds projected for the city?

Adequate analysis will include not only worthwhile projections of when technological advances may occur, but data and calculations concerning related JANUARY 1978

questions and comprehensive plan- ning for the city as a whole. Statis- tical correlation, probabilities of occurrence for single and condi- tional events, logical constructs, and structured judgments on many more matters than technological developments will be required.

16. Analytical treatment of indefinites As more numerical data are employed to describe

urban activities and as municipal operations become increasingly scientific and technical, quantification and mathematical calculation are clearly essential for successful city planning.

There are, of course, important elements and aspects of cities which are not susceptible to quantitative meas- urement and mathematical treatment in the same way as components which are reliably represented by numbers. Among the elements difficult to quantify are beauty, design, contentment, unrecognized stresses and strains, environmental amenity, and various forecasts of events or conditions. There are also crucial interrelationships among elements which cannot now be calculated mathematically: such as the social, psychological, and physical effects of dense concentra- tions of urban buildings upon their inhabitants; the quantitative relationship between traffic congestion in downtown areas and population density, coverage on the land with buildings, and floor-area ratio; the combined effects on the urban environment of diverse activities and projects; or numeration of the costs and benefits of an urban project or activity beyond a few first-order effects and interrelation- ships.

One way of incorporating elements which cannot be directly quantified is to elicit and program human judgments as part of the logical formulation or mathematical statement. The Delphi technique is such a process, structured to ascertain the respective opinions of a selected group of experts and determine their collective judgmental conclusion. O r the par- ticular effects of an unquantifiable element in an otherwise calculable sequence of cause and effect can be approached if a range of possible consequences can be introduced which helps those who must make a final decision to reach a subjective conclusion.

Are there ways of numerically and mathematically combining in an analytical construct simulating the city’s functioning, to be used in comprehensive city planning: the quantifiable and the indefinite, the scientific and the nonscientific, the rational and the irrational, the predictable and the unpredictable, new approaches such as fuzzy mathematics or the mathe- matics of catastrophe with established mathematical formulations? Can the representative validity and

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practical usefulness of such an analytical construct be maintained as the breadth and depth of the multitude of interrelationships be- tween disparate elements are suc- k-1 cessfully identified?

17. Continuity of planning Plans are frequently drawn for one of three time

periods, variously labelled: ( 1) short-range, near-term, current, operating, tactical; (2) medium-range, mid- term, intermediate; (3) long-range, long-term, master, strategic, policy. Whether these plans for particular periods of time are divisible or continuous is an important question for both planning theory and practice. Different presumptions concerning the capability to forecast and shape the future are in- volved. There are significant differences in the amount and frequency of information needed, the extent of real-time continuing analysis, organization for planning, the kinds of planning required, decision-making procedures, means and methods of effectuation, and the role of city planning in govern- ment. Are legislative decision, city management- administration, and city planning distinct endeavors or parts of a single continuum of analytical con- sideration and implementing actions?

One view maintains that plans for different time periods are interrelated but can be formulated and acted upon separately. Short-range plans program current operations in detail. Long-range plans present policies, objectives, and courses of action directed toward a desired end state for the organism many years hence. Since it is believed that this end state can be conceived today, the strategic plan will retain its relevance during the extended period projected for its attainment.

A differing view sees planning as a continuous process and plans for designated periods of time as inseparable. Operating plans are drawn to attain the ends determined desirable for the future, and long- range plans must relate to the realities of the present and represent the accumulation of accomplishments called for in short-run and intermediate plans. But unanticipated developments and unpredictable events will occur frequently within the organism being planned and its environment. Therefore, short-, inter- mediate-, and longer range plans must all be changed or adjusted to some extent because they are analytically and operationally interdependent.

18. Plan change The relation of different kinds of plans to real

time varies widely. On the one hand, end-state master city plans portray the proposed physical-spatial features of the community twenty or more years in the

future. Ordinarily, the progressive stages of develop- ment to achieve this end state are not indicated; it is presumed that whatever actions are necessary will be taken or will occur. This kind of plan, which is still the most common form for city planning in the United States, is redone every ten years or so when funds can be found for the thousands of man hours and several years required.

On the other hand, planning by municipal depart- ments concerned with transportation or energy, for example, involve monitoring-control mechanisms which observe traffic conditions or the flow of energy, and adjust operations accordingly. Short-range plans depend on the continuously observed situation, and longer range plans are revised immediately as trends are revealed, unanticipated developments or events occur, or new needs or objectives are established. Operational adjustments are made continually, and the uninterrupted accumulation of information and monitoring of relevant events usually results in frequent modification or change of intermediate and longer range plans.

How often plans should be altered is a basic analytical question in all forms of planning and human endeavor. Failure to change when conditions change significantly invalidates a plan or effort. Re- peated change interrupts the progressive sequence of actions called for and thereby increases costs and delays and impairs or prevents attainment of the results intended. Modifications, however, are almost always possible because they are adjustments of the existing plan rather than its reformulation into some- thing different.

There is a point in the implementation of all plans when further change is unproductive, unless the situation has changed so drastically that the plan should be abandoned. After this “point of no return,” the altered situation is taken into account in another or subsequent plan. Cost-benefit concepts are in- volved. How much time, money, energy, and motiva- tion have been expended? How much of this would be wasted by revision of the plan and how much additional time, money, and planning would be required for a new plan? Do the discounted prospects of a new or revised plan exceed the projected prospects of the existing plan and the cost of a new one? An analytical subsystem to answer these questions is needed as part of the larger system of compre- hensive city planning and decision making.

19. Citizen participation in city planning There has been considerable discussion in recent

years concerning greater participation in city planning by individual citizens and neighborhood groups- represented by professionals if need be. Proponents of this view maintain that local governmental decision makers and bureaucracy are becoming more and

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more divorced from the needs, desires, problems, and objectives of those they represent and serve. This is felt most strongly to be the case for minorities, the disadvantaged, and the powerless. It is contended that procedurally plans are imposed from the “top down” rather than formulated from the “ground up.”

On the other hand, it is generally recognized that technological developments require an increasing degree of overall, or central, planning and decision making to provide essential urban utilities and services efficiently and equitably. Planning and carrying out most functional activities and projects are requiring longer and longer periods of time. Plans and programs for most environmental problems such as air, water, and noise pollution involve metropolitan or regional areas which are rarely coterminous with the political boundaries of the different governmental jurisdictions within the larger geographical area of environmental impact.

Citizen participation is an analytical as well as representational, political, and social question. In- formational requirements, analytical methods, public exposition, and the organization of urban planning vary with the nature and extent of participation by people in the process.

Is the knowledge necessary to conduct society becoming more and more detailed, technical, and complex? Will fewer and fewer individuals and groups be able to comprehend, integrate, and manage societal components? What is the best way of incorporating the needs and desires of people in the analytical process of planning a city-without their having to acquire special knowledge, develop technical under- standing, and participate more often than most citizens want to or can afford? Are only the inhabi- tants of each governmental jurisdiction to be con- sidered and to participate in its city planning, or are others living beyond its boundaries but directly or indirectly affected entitled to be included in the analysis and to participate in the formulation of plans?

20. Analytical simulation of the city The most critical requirement for enlightened

municipal management and city planning is an analytical formulation, model, or simulation which accurately represents the structure and functioning of the city as a whole. Without this analytic instrument, the most basic purpose of planning-the optimal allocation of resources-cannot be properly per- formed. The probable effects of policies, decisions, and plans for one urban component on other components with which it is related cannot be determined beforehand. Without it, subjective judg- ment, intuitive opinion, or best guess must be employed by themselves without benefit of analysis, with the greater likelihood of serious and irreversible

JANUARY 1978

mistakes through disjointed plan- ning and actions.

The basis for such an analytical simulation will be a logical construct of urban components and their interrelationships. This must be preserved throughout subsequent expansions and improvements of the model. To the extent possible, the simulation should be expressed quantitatively and mathematically: to facilitate measurement, correlation, integration, and projection; and to permit the applica- tion of scientific method whenever feasible. Because not all urban elements can be quantified, the struc- tured judgment of selected people, public opinion, and other subjective evaluation must be incorporated as integral parts of the simulation.

Development of the model must begin with a few components which are well understood and can be expressed and integrated quantitatively. Additional elements, further information, and more complex analysis are incorporated into the model only when this can be done without impairing the accuracy already established for individual elements and their respective interrelationships already calculated. Since each additional element may alter one or more of the interrelationships previously established, the total calculative modifications required may be many more than the cumulative sum of crosscorrelations.

Because a city is such an enormously complex organism with so many different components and aspects, a successful analytical simulation is a most difficult long-term endeavor. But if soundly con- ceived, the simulation can be used to advantage from the beginning. In business, three formulations- operating and profit-and-loss statements and the balance sheet-can be used to conduct the enterprise successfully until the additional information and analysis required for more than minimum simulation can be developed and integrated with these three accounts.

21. Analytical core for municipal management

As indicated immediately above, formulation of an analytical simulation of a city’s structure and func- tioning must begin with a few components and their interactions. Additional elements are incorporated into the simulation as they meet agreed upon standards of accuracy and can be integrated with the interrelationships already calculated. From the first stage of its formulation until the distant day when a completely representative model may be devised, any simulation of the city is necessarily incomplete. But not to use available urban knowledge because it cannot be totally comprehensive would be self- defeating.

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It is therefore important to know which components and interrela- tionships most usefully simulate the city for operational rather than research purposes. This simplifica- tion is essential for the small com- munity which can afford only mini- mum data gathering and analysis. For the funds available, which

components should it select and what calculations should it maintain continually up-to-date as back- ground for study and decision?

This core will of course vary among different types and sizes of communities, their stage of develop- ment, and historical circumstances. But undoubtedly a number of components and interrelationships will be common to many, if not most, communities: for example, data and analysis concerning population, transportation, land use, and the source and applica- tion of municipal funds.

From the most advanced simulation of a city developed by research devoted specifically to this end -usable perhaps only by larger cities-the most indicative elements and interrelationships can be identified. This simplification would make possible upgrading municipal management and introducing city planning for the first time in communities so inclined.

I t would be equally useful for the many municipali- ties in the United States which for years have had city planning, but in name only with no real influence on legislative leadership, executive management, or functional departments-and consequently little effect on directing the development of the city. T o replace periodic end-state master planning with more effective continuous city planning requires an analytical core as a central feature which is used regularly by those directing and planning the city.

22. Display of information and analysis Until now the product and proposals of city

planning have been formulated and presented as graphical displays, written documents, and printed publications. These serve the purposes of the periodic end-state city planning commonly practiced in the United States, but their use by municipal decision makers and their influence on the direction of cities have been minimal.

If city planning analysis and recommendation must be more closely related to municipal decision making and real time as some people maintain, different methods of displaying information and analysis are required. The drawings and writing now widely employed cannot be revised quickly enough because drafting, reproduction, and printing are time consum- ing and expensive-so much so that there is inevitably resistance to repeated revision.

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Informational and analytical displays can be made more flexible by stick-on letters, numbers, and tapes, and erasable surfaces and markers. Numerical and written data can be portrayed mechanically or elec- tronically. Graphics can be shown and changed quickly on cathode-ray tubes and as computer print-outs.

There are many information, planning, or control centers with display devices suited to the particular operational and planning purpose. Oil refineries, utilities, and other continuous process industries employ sensing instruments and display devices to monitor and simulate the operating system, and allow immediate changes in production or the correction of malfunctions. Centers for corporate planning analysis by business have been developed in recent years. The military services have many command and control centers. The National Aeronautics and Space Administration space center directs missions in real time, simulating them for planning purposes before, during, and after actual flight.

Display methods must of course be fitted to the organism or system being planned. They must be understandable and acceptable to decision makers, accurately represent what they are intended to simulate or portray, permit changes of information and analysis as needed, meet cost limitations, and fulfill other general requirements for effective display.

These considerations raise the important question of what kinds of displays are best suited to portray information and effect integrative analysis for dif- ferent applications, stages, conditions, and kinds of planning.

23. Evaluating the effectiveness of planning

The effectiveness of a specific plan for a project, single function, or particular activity which involves a physical product or discrete output can usually be determined. Whether what was prescribed in the plan was attained can be directly observed; or conditions before and after can be compared if reliable units of measurement were part of, or a reason for, the plan in the first place. Collective judgment can also be employed.

It is when the plan is multipurpose or compre- hensive in intent and coverage that its consequences are difficult or impossible to identify. Tracking the enormous number of repercussive effects brought about by the many actions called for by a compre- hensive plan requires greater knowledge of the complex interactive functioning of the urban or- ganism than is now available. Units of measurement which can be used to evaluate single-purpose projects or activities do not apply as more and more disparate but interrelated economic, social, political, psycho- logical, cultural, and other effecB are considered. Separating the impacts of the many elements and

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forces involved quickly becomes analytically impos- sible; cause and effect cannot be traced precisely.

Other considerations complicate evaluation in con- tinuous comprehensive planning. Since conditions never remain constant while a plan is being realized, it is difficult to determine to what extent its success or failure is the result of developments within the organism or its external environment which were not part of or taken into account in making the plan. If a plan is modified frequently, the specific consequences of each successive version are obscured. And plans incorporating general policies or intentions which are carried out as opportunities arise are difficult to assess because implementing actions are unstated, unpredetermined, and different.

It is often difficult to determine-much less measure- the effectiveness of plans which were originally developed by central staff but were taken over, changed, and effectuated by a line organization. The staff planner may deliberately give credit for the plan to a legislator or line executive to obtain acceptance and necessary support.

Is there a way of tracing and measuring the many

different effects of a composite or comprehensive urban plan so that its effectiveness can be evaluated conclusively? Or is the organismic complexity of cities such that only limited evaluation will be possible for a long time to come? Is the knowledge required for complete evaluation theoretically infinite and therefore unachievable?

* * * The resolution of any one of these unsolved

problems of urban planning theory and analysis will constitute a significant contribution to knowledge, ensure a successful career for the person providing an answer or solution, and probably secure for him or her a place in the history of the development of urban planning thought. When all twenty-three prob- lems are resolved, city planning will be established beyond any reasonable doubt as a vital intellectual discipline and foremost field of knowledge.

Notes 1. David Hilbert, 1902, Mathematical problems, Bulletin of lhe

American Mathematical Society 8: 437, as translated for the Bulletin by Dr. Mary Winston Newson from the Gottinger Nachrichten, 1900, p. 253 and the Archiv der Mathematik und Physik, 3rd

series, vol. I , 190 I , p. 44.

2. Constance Reid, Hilbert (New York, Heidelberg, and Berlin: Springer-Verlag, 1970), p. 70.

Conference Calendar (Continued from p. 46)

Sept. 14-19

Sept. 27-Oct. 1

Oct. 1-6

Oct. 8-11

Oct. 11-15

Annual Convention, American Public Works Association, Boston. Contact: A.P.W.A., 1313 E. 60th St., Chicago, Ill. 60637

Annual Conference, American Institute of Planners, Hyatt Regency Hotel, New Orleans. Contact: AIP, 1776 Massachusetts Ave. NW, Washington, D.C. 20036 Annual Conference, Water Pollution Control Federation, Anaheim Convention Center, Ana- heim, Calif. Contact: Robert Canham, W.P.C.F., 2626 Pennsylvania Ave. NW, Washington, D.C. 20037 National Conference, National Association of Housing and Redevelopment Officials, Olym- pic Hotel, Seattle. Contact: NAHRO, Suite 404, 2600 Virginia Ave. NW, Washington, D.C. 20037 Annual Convention, National Trust for His- toric Preservation, Drake Hotel, Chicago. Contact: N.T.H.P., 740-748 Jackson PI. NW, Washington, D.C. 20006

Oct. 15-19 Annual Meeting, American Public Health Association, Los Angeles. Contact: A.P.H.A., 1015 18th St. NW, Washington, D.C. 20036

Oct. 15-19 Annual Meeting, National Recreation and Park Association, Miami Beach. Contact: N.R.P.A., 1601 N. Kent St., Arlington, Va. 22209 First National Conference on Urban Design, New York. Contact: Lois Heyman, Urban Design, 355 Lexington Ave., New York, N.Y. 10017 212/682-0830 14th American Water Resources Conference, Dutch Inn, Orlando, Fla. Contact: Dr. Melvin W. Anderson, Dept. of Structure, Materials and Fluids, University of South Florida, Tampa, Fla. 33620

Oct. 18-21

Nov. 6-10

We would like to receive notice of major conferences for possible inclusion. Due to limited space, the selection of announcements will undoubtedly be unreasonable, arbitrary, and capricious.

I T h e AIP Planning Policy and Government Relations Conference previously announced for I March has been cancelled.

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