Chủ Nhật, 29 tháng 6, 2014

QUY HOẠCH CẢNH QUAN ĐÔ THỊ- HÌNH ẢNH ĐÔ THỊ


Paul D.Spreiregen
Summary
Architectural design begins with the preparation of a building program and site analysis. So, too, do plans for designing or redesigning a portion of a city, In the case of a city, the analysis is a diagnosis of the city’s component pieces, to see the relations between these pieces and to assess their condition, A visual surveyin urban design is an examination of the form, appearance, and composition of a city—an evaluation of its assets and liabilities. A visual survey also enables the urban designer to see where the city needs reshaping.
Key words
actvity, density, district, image, route, scale, skyline, traffic pattern,
urban structure, visual survey, vocabulary of urban form
Credits: This article is a chapter of the author’s writings, Urban Design, published by the American Institute of Architects and McGraw-Hill, 1965, and first appeared in AIA
Journal,S 1964. Drawings are by the author.

Making a visual survey
A Working Vocabulary of Urban Form
Architectural design begins with the preparation of a building program and site analysis. So, too, do plans for designing or redesigning a portion of a city. In the case of a city, the analysis is a diagnosis of the city’s component pieces, to see the relations between these pieces and to assess their condition. A visual survey in urban design is an examination of the form, appearance, and composition of a city—an evaluation of its assets and liabilities. A visual survey also enables us to see where the city needs reshaping.

A visual survey can be made of any city or town, regardless of size. It can also be made at different scales—a neighborhood, the center, a suburban area, or a small group of buildings. Furthermore, it can be made for a built-up part of the city which is going to be altered very slightly or for a part of the city which is going to be
rebuilt entirely. The process of making a visual survey is not complicated, nor need it be done with a high degree of precision. As a matter of fact, it is best done in general terms, for to deal with the city on a large scale we must think broadly.
To conduct a visual survey, one must have a basic idea of the elements of urban form. These necessitate a descriptive vocabulary.


Next, one must examine the city and describe it in terms of this vocabulary. It is also necessary to relate the elements, in order to understand its workings, its form, and its consequent appearance. While making a visual survey, it is important to constantly evaluate. Certain discordant elements must be noted as faults to be corrected; certain appropriate elements must be noted as assets to be protected. A good urban design survey will also disclose a number of specific ideas for improving, correcting, or replacing parts of the city, for a good survey leads to ideas for action.
The Image of the City.
People’s impressions of a building, a particular environment, or a whole city, are, of course, more than visual. Within the city lie many connotations, memories, experiences, smells, hopes, crowds, places, buildings, the drama of life and death, affecting each person according to his particular predilections. From his environment each person constructs his own mental picture of the parts of the city in physical relationship to one another. The most essential parts of an individual’s mental image, or map, overlap and complement those of his fellows. Hence we can assume a collective image-map or impressions-map of a city: a collective picture of what people extract from the physical reality of a city. That extracted picture is the image of the city.
Every work of architecture affects the details and often the whole of the collective image. The collective mental picture—the image of the city—is largely formed by many works of architecture seen in concert or in chaos, but definitely seen together.
Several years ago, Prof. Kevin Lynch conducted a study of what people mentally extract from the physical reality of a city. He reported the results in a book called The Image of the City, and his findings are a major contribution to understanding urban form and to architecture as component parts of that form. Professor Lynch is one of the country’s leading investigators of urban form. Many of the ideas in this book were derived from his studies. In his examination of the form of the city, Professor Lynch found that there are five basic elements which people use to construct their mental image of a city:


Pathways: These are the major and minor routes of circulation which people use to move about. A city has a network of major routes and a neighborhood network of minor routes. A building has several main routes which people use to get to it and from it. An urban highway network is a network of pathways for a whole city. The footpaths of a college campus are pathways for the campus.
Districts: A city is composed of component neighborhoods or districts; its center, uptown, midtown, its in-town residential areas, trainyards, factory areas, suburbs, college campuses, etc. Sometimes they are distinct in form and extent—like the Wall Street area of Manhattan. Sometimes they are considerably mixed in character and do not have distinct limits—like the midtown area of Manhattan.
Edges: The termination of a district is its edge. Some districts have no distinct edges at all but gradually taper off and blend into another district. When two districts are joined at an edge they form a seam. Fifth Avenue is an eastern edge for Central Park. A narrow park may be a joining seam for two urban neighborhoods.
Landmarks: The prominent visual features of the city are its landmarks.
Some landmarks are very large and are seen at great distances, like the Empire State Building or a radio mast. Some landmarks are very small and can only be seen close up, like a street clock, a fountain, or a small statue in a park. Landmarks are an important element of urban form because they help people to orient themselves in the city and help identify an area. A good landmark is a distinct but harmonious element in its urban setting.
Nodes: A node is a center of activity. Actually it is a type of landmark but is distinguished from a landmark by virtue of its active function. Where a landmark is a distinct visual object, a node is a distinct hub of activity. Times Square in New York City is both a landmark and a node.

These five elements of urban form alone are sufficient to make a useful visual survey of the form of a city. Their importance lies in the fact that people think of a city’s form in terms of these basic elements. To test them, sketch a map of your own city, or better still, ask someone else to do it, taking only a few minutes. The result will be two fold: a picture of the most salient features of a city’s form—its image—and a map of the sketcher’s particular interests as they relate to the city. The result will also be akin to the cartoon maps of the United States as seen through the eyes of a Texan or a New Yorker. The features will be distorted and probably exaggerated, the degree of distortion reflecting the hierarchy of values of the sketcher. The more “imageable” a city, the easier it is to find one’s way about in it, even if its street pattern is not clear. In designing a city, it is important to consider how a new development will affect the total urban image. A new development can be made to tie visibly into a city’s path system; to form or help reinforce a district; if on an edge, to strengthen the edge; and if at a seam, to maintain continuity. It can also become a good landmark and an active node.
Paths, landmarks, nodes, districts, and edges are the skeletal elements of a city form. Upon that basic framework hangs a tapestry of embellishing characteristics which all together constitute the personality of a city. To build a broader vocabulary upon this basic framework we must consider landform, natural verdure, climate, several aspects of urban form itself, certain details and several lesser facets of form.
Landform and Nature
Every city is built on a piece of land. The form of this land and its features are the foremost determinants of a city’s form. In speaking of landform, we are speaking primarily of topography.
In looking at landscape, we are seeking its character. As urban designers we observe the form of the terrain—flat, gently rolling, hilly, mountainous—in relation to the architecture and the cities which are set in it. A flat site may suggest either vertical architecture or assertive horizontals. A slightly hilly site may call for vertical architecture at the summits with a flow of cubes on the slopes, or may suggest a termination of architecture just below the crests. A steep hillside or valley may lend itself to terracing, with orientation to the sun. In every case we must assess the qualities of the terrain, including the design relationships they express. The prominent features of a landscape should be carefully noted— cliffs, mountain peaks, ranges of hills on the horizon, plateaus, rivers, or lakes. These are accenting landscape features which can be employed actively as sites or passively as vistas, supplementing architectural and urban form. They can be used as major vista objectives from points within the city or as special sites for buildings. Some are better left in their natural state.
Indigenous greenery should be assessed in terms of shape, size, character, practicability, and seasonal change. An urban designer needs a working knowledge of the local flora and its suitability in various uses. A thickly foliated tree, formally shaped, might be proper for lining a road to shield the automobilist from a low sun. A spreading shade tree of informal shape, might be quite appropriate as a restful sitting place in the bustle of the city.
Characteristic detail of the landscape should be considered for possible use as architectural and urban design embellishment: a native rock or gravel, a characteristic earth color, the form of local streams, characteristic stands of trees. Indigenous architecture should also be noted, particularly in older towns. These are the result of evolution and may have achieved a mature relationship with their environment.
Certain areas of landscape should not be touched, but preserved in their natural state. A survey of the natural landscape may disclose areas which are better left as wilderness. These might well be chosen with relation to nearby cities and towns so that they are accessible as necessary complements to urban life, but not menaced by it. Buildings and small towns can often be seen in their entirety in the framework of nature. As such, they are accents or counterpoints to their natural settings, elements of vitality in a setting of repose. A larger town, however, can seldom be seen in its entirety, but only in part, from various viewing places. Here we have a one-to-one relationship, nature being less a setting than a major component of the whole scene—balancing the sight of the city rather than acting as a setting for it. Raw nature sometimes exists within large cities in the form of streams, rivers, shore lines, cliffs, etc. Here the city is the setting for nature. Nature, in this circumstance, becomes a foil or counterpoint to the urban surroundings.
Thus, we might regard a small town as an object in the embrace of nature, a larger town as being hand-in-hand with nature, and finally, the large city as assuming the role of nature and becoming the embracer.
A visual survey of nature in relation to achitecture and urban design is threefold in scope. We first try to determine the character of the surrounding landscape to which our architectural and urban forms must respond esthetically and functionally. Second, we evaluate the degree to which our existing architecture and cities enhance nature.
Third, we must decide what natural areas are to be left alone to act as complements to urban form. Throughout this process we search for assets and liabilities, preserving and enlarging upon the one and noting corrections to be made on the other.
Every work of architecture affects the natural landscape either positively or negatively; so does every structure and human settlement. Nature, in turn, as a setting for our constructions, is a visual framework to which all our constructions must respond.
Local Climate
While on the subject of the natural features of the terrain, it is wise to check on local climatological conditions. Local climate determines much of the character and appearance of the landscape and buildings.


The following aspects of climate can be readily found in United States Weather Bureau publications. Temperature: Seasonal temperature and humidity as averages and extremes which indicate the periods of relative comfort, the extremes which must be ameliorated, and which therefore determine architectural and urban form.
Light: The number of clear, partly cloudy, and fully cloudy days, which conditions the light affecting the appearance of the city and of buildings.
Precipitation: The amount of precipitation in the form of rain and snow.
Sun: The angles of the sun in different seasons, which affects viewing conditions and, thus, design. It is useful to make a simple three-dimensional model to study these angles.
Winds: The prevailing seasonal winds including the direction and intensity of cold winter winds, gentle or severe fall and spring gusts, and cooling summer breezes. These affect design considerably.
In addition to these quantitative factors there are a number of qualitative aspects of climate which are as important in urban design. Some cities are well oriented toward the rising sun or the setting sun. Some cities have forms that derive almost directly from their climates— arcaded cities in the sun, for example, Considerable research or experimentation might be done to determine how cold winter winds could be slackened and cooling summer breezes induced. The quality of light—sharp and clear or cloudy and dull—should be a determinant in the design of building facades including their degree of intricacy and their coloring. These are always a matter of artistic consideration but a careful appraisal of actual conditions can help a decision.
Shape
Every city has a general overall shape. There are several classifications of shape.
Radiocentric: The most frequently found urban form is the radiocentric, a large circle with radial corridors of intense development emanating from the center.
Rectilinear: A variation on radiocentric form is the rectangle, which usually has two corridors of intense development crossing at the center. This variant of the radiocentric form is found in small cities rather than large. It is the radiocentric form with right angles.
Star: A star shape is a radiocentric form with open spaces between the outreaching corridors of development.
Ring: A ring shape is a city built around a large open space. The San Francisco Bay is such an open space for the cities of the bay area. A ring and star may be found in combination, particularly where a loop road is built around the outskirts of an expanding metropolis.
Linear: The linear shape is usually the result of natural topography which restricts growth or the result of a transportation spine. Stalingrad in the Soviet Union was planned as a linear city. The megalopolis on the East Coast has become a vast metropolitan area with a linear configuration.
Branch: The branch form is a linear spine with connecting arms.
Sheet: A vast urban area with little or no articulation. Articulated Sheet: The articulated sheet form is accented by one or more central clusters and several subclusters.
Constellation: The constellation is a series of nearly equal-size cities in close proximity.
Satellite: The satellite is a constellation of cities around a main center.
These classifications of form have definite implications for a city’s function. They have advantages and disadvantages related to circulation, proximity to open space, and articulation of neighborhoods or districts. Further, these classifications may be applied to the city as a whole or to parts of the city, isolated for study, like open spaces or circulation. The open spaces of a city may be linear or branched; or they may form a radiocentric pattern. The circulation networks may likewise be described as one or another shape.
Size and Density
Closely related to a city’s shape is its size, a quantitative aspect which can be approached several ways. We first of all think of the physical extent of a city: so many miles across or so many miles from center to outskirts. We can also describe size in terms of the number of inhabitants. The relation between size and density is important, for it indicates the distribution of people and the city’s urban massing.
Density can be computed mathematically in several ways: the number of people per square mile; the number of houses per acre or square mile; or the amount of building floor area in a given section. It can also be expressed in terms of automobile population. In 1962 Los Angeles, the country’s most auto-oriented city, had 2,220 cars per square mile and Washington, D.C., had 4,100 cars per square mile. This comes as a surprise to most people. One would think that those figures are reversed—which suggests a note of caution in judging aspects of quality from statistics of quantity. The gross size of a city in terms of its population is also revealing.
Classifications according to size alone are quite useful. A basic population of about 200,000 to 300,000 is necessary to support basic public cultural facilities. Amsterdam, Holland, with a population of about a million people, is of the maximum size that can be traversed on foot by a hearty walker, from center to outskirts. Unless a city is evenly built-up, studies of density are best made on separate sectors of a city. Density figures indicate the relationship between built-up and open land; therefore they can describe almost graphically the image of a suburban residential area or an in-town row-house area. Densities have definite implications for various forms of transportation. In making a visual survey, it is helpful to determine the density of various areas and to relate the density figures to physical patterns of land and buildings and, hence, the visible
form of the area.


Pattern, Grain, and Texture
Urban areas have distinct patterns. Usually these are seen in their block and street layouts. Most American cities have rectilinear block and street patterns. On rolling terrain, in outlying areas, curvilinear streets and blocks form another type of pattern. A cul-de-sac system forms a third pattern. Mixtures of open space and built-up space constitute still another pattern. A basic design pattern can be very helpful in planning a residential area or a campus area. An urban pattern is the geometry, regular or irregular, formed by routes, open spaces, and buildings.
Grain is the degree of fineness or coarseness in an urban area.
Texture is the degree of mixture of fine and coarse elements. A suburban area with small houses on small plots has a fine grain and a uniform texture. With small houses on varying size lots, it could still have a fine grain but an uneven texture. In the city, large blocks with buildings of varying sizes could be described as having a coarse and an uneven texture. If the buildings are uniform in size, they could be described as having a coarse grain but a uniform texture.
Such distinctions are easily indicated on a sketch map. They are useful in evaluating an area’s form and in making decisions about a design treatment for it. For example, a coarse-grained unevenly textured area may be impersonal and repellent and could be treated with some fine scale and unifying design elements, An extensive and uniformly-grained area might well be treated with relieving accents.

Urban Spaces and Open Spaces



Urban shape, pattern, grain, size, density, and texture are primarily aspects of solid form—the building masses of the city, In architecture it is rather helpful to conceive of a building not only as a solid but as spaces modeled by solids. It is also helpful to consider a city this way. The spaces of the city range from the space of the street to the space of a park system and, ultimately, to the vast space in which an entire city exists. It is helpful to think of these spaces as two generic types: formal or “urban spaces,” usually molded by building facades and the city’s floor; and natural or “open spaces,” which represent nature brought into, and around, the city.
Basically an urban space must be distinguished by a predominant characteristic, such as the quality of its enclosure, the quality of its detailed treatment or outfittings, and the activity that occurs in it. An urban space should, ideally, be enclosed by surrounding walls, have a floor which suits its purpose, and have a distinct purpose to serve.
If, however, any one of these qualities is sufficiently strong, it alone may establish the sense of urban space.
A group of office buildings may contain a space around a poorly designed plaza or a complex road intersection, the floor space being devoted entirely to traffic. This is an urban space which has a sense of place in the city. It is both a landmark and a traffic node, as well as an office node. An urban square may be beautifully landscaped as a restful urban park, but it may lack entirely the peripheral building facades which are needed for a sense of enclosure.
Here we have a poorly enclosed space, but a space nevertheless. In another instance, a particular place in the city may function as the locale of an important activity while possessing neither physical enclosure nor appropriate floor. Times Square in New York is such an example.
In all these examples we have a sense of space. Such spaces are islands or oases in the city. But urban spaces can also be linear corridors.
Avenues and streets are linear urban spaces if they are enclosed on two sides or have some element of unifying character—trees or uniform buildings. Corridor spaces are spaces for linear movement. Island or oasis spaces are stopping places. Of course the two can be interconnected. In fact, a spatial structure for an entire city is exactly such an arrangement at the city’s total scale. Open spaces, being nature brought into the city or open expanses allowed to remain in their original state, cannot be described in quite the same manner used for urban spaces. Their scale is given by the trees, shrubs, rocks, and ground surface rather than their gross width and length. Their appearance is characterized by the sight of natural verdure rather than surrounding buildings. However, a vista of a distant building may accent a particular spot and a bridge or pathway may complement nature’s forms. Open spaces in the city have a wide variety of purposes. They are a complement and foil to urban form. They are also reservoirs of land for future use. For an urban design survey, one should study the spaces of the city as an overall structure. In doing this it is helpful to classify spaces according to their actual use and to consider formal urban spaces and the natural open spaces together.
For example, one could start by mapping all the recreational parks in the city, then the interconnected stream parks. The center city urban parks could be mapped, and the main corridor spaces that lead to them or connect them. The nodal spaces as well as the connector spaces all together would form the spatial network. Such a survey would disclose a need for creating spaces in certain areas, a need to improve existing spaces, and some possibilities for connecting all of them. The survey of spaces should disclose a hierarchy of spaces for rest and repose to spaces for meeting and bustling activity.
A city’s entire system of public lands—roadways, schools, parks, civic buildings, libraries, etc.—could be thought of as an open space network possibly complemented here and there by public buildings. In an urban design survey we look for the location, quality, and amount of open space in relation to the city’s built-up areas.


Routes
Landscape, architecture, and cities are seen as sequences as we travel along routes of movement. Routes of movement affect considerably the appearance of the landscape through which they pass and the architecture and cities which they serve. Routes of movement are a principal determinant of urban form. In making an urban design survey of the routes of a city, one should begin with the area well beyond the city limits, far out in the country. The primary function of a highway is to allow traffic to move, but a large part of that job depends on how clear the route is in relation to the city. This aspect of highway engineering—the “image-ability” of the highway—is a matter of revealing its clarity of form and direction to the user. Too many highways have very poor physical relationships to the areas they serve. Rather than helping to define these areas, they often slash through them, actually acting as a blighting and disintegrating force.
Routes in the Countryside
In the open landscape, existing and proposed routes should be examined and assessed with a view to how well they relate to the natural terrain. How artfully or awkwardly do routes traverse the landscape, revealing its prominent features? Are vistas taken advantage of, or ignored? Some vistas might well be presented with dramatic suddenness; others might be introduced gradually, or be seen only in part.
Are there dull areas which require embellishment? Perhaps the introduction of a curve or rows of trees and shrubs could give more visual interest. Are there obstructions to the enjoyment of the prominent natural features? Does the road itself and its furniture mar the landscape or add beauty to it?
The outlying routes of your city are the first introductions which approaching visitors receive, giving them their major impressions. In making a visual survey of routes, the routes should be charted, noting the character of the terrain and the adaptation of the roads to it, the artful dramatization of landscape features, the quality of added features, the accenting of the route, its faults and possibilities for improvement or correction. Every new route should be examined and
designed on these bases as a matter of sound road engineering.
Approach Routes and Surface Arteries
Approach routes present cities to us. They must satisfy the visual requirement of presenting architecture and cities in their best light, while enabling us to find our destination readily. The two requirements go hand in hand. An approach route must both inform us and conduct us.
The major routes through the city are surface arteries—highvolume traffic streets which carry buses and autos. They can be evaluated according to how they tie into the expressway pattern, their clarity of form, their relation to the cityscape, the shape of the building sites they pass by, and the way they pass through existing districts.
Another consideration is the street furnishings of the major surface streets. Can their design be improved and a program for improving signs and traffic furniture be started? How well do the through arteries tie into the pattern of slower-speed local streets? How well do they tie into major garages and parking areas? How easy is it to find a garage near your destination and to get into and out of it? Most important of all, we must examine the relation between a street’s traffic and buildings. A good index is the degree to which street traffic is actually serving the buildings on the street, in contrast to traffic which is merely passing through on the way to some other destination.

Local Streets
The through arteries serve an intricate network of small streets, along which cars, buses, and delivery trucks stop and go. These streets carry a mixture of vehicles and people. In surveying them, we examine whether vehicular and pedestrian movement are in conflict with each other or aiding one another. Where do they belong together and where not? Are pedestrians forced to wait for long periods of time to cross streets, or are pedestrians free to cross streets anywhere? Is safety achieved by the use of stoplights or by grade-separated pedestrian crossings? Is the vehicular traffic strictly local, or is much of it through traffic? Can this through traffic be relocated? How can existing small streets be protected against the intrusions of through traffic? What is the dimensional scale of the intimate local streets? How do they relate to the size of their districts? Can these patterns be improved and strengthened?
These comments illustrate that an inquiring survey raises many questions and stimulates many ideas. As we elaborate on the pathdistrict-edge-landmark-node framework, we find that some of them require more attention than others. Degree of emphasis on one aspect or another will depend on the size of the city or the urban sector being surveyed. On the large-scale survey of the whole city, its paths, districts, and open spaces, for example, may be the predominant elements. However, at all levels, the examination of the districts of the city will probably require the greatest effort.



The Districts of a City
Every city consists of a series of parts which we refer to as districts or enclaves or sectors—or perhaps as quarters, precincts, or areas. They are distinguishable in that they have dominant and pervasive characteristic features. Our mental images of cities consist, to a large extent, of the arrangement of these parts. Some are distinct, some overlap others, some are uniform, some are very complex. Almost all are in a process of change, which further affects their appearance and their size. A very small town has at least several distinguishable areas; a metropolis may have fifty or a hundred. The pattern of districts is closely related to the pattern of routes. The size of a district may be determined by the nature of the internal routes serving it. A commercial center, for example, can usually be traversed on foot or by a short cab ride. A residential section may often have local community facilities which can be reached on foot, although its gross size may be far beyond the limits of pedestrian traverse.
The districts of a city vary considerably in their strength of character. Districts which do have very strong characters often develop identifying names—Wall Street, Georgetown, Beacon Hill, Greenwich Village, the Loop. Other districts with less assertive character often bear names related to their historic origin—Market Street or Main Street, Foggy Bottom, Silver Spring, Brookline. American cities, like most cities of the world, reflect their characteristics of culture, growth, and development in an urban nomenclature.
In the United States this nomenclature includes: “downtown,” the original center; “uptown,” the enlargement of the original center; “midtown,” an offshoot of both; “Chinatown” and “Harlem,” ethnic areas; “the other side of the tracks,” characterizing poor residential areas in the shadow of factories; “the waterfront”; “the outskirts.”
Basically, there are two things to look for in discerning the various districts of a city: physical form and visible activity. For example, in a commercial center the types of buildings, the signs, the demolition and construction activity, the crowds of rushing people, the cabs and buses, the parking facilities—all these identify the place for us.
On the other hand, in a residential area we have the houses, their spacing, the trees, the milk wagons, the parked cars, the children playing, the occasional neighborhood stores and schools. The sum impression of the individual parts and their relationships conveys to us the existence of a particular district of a city—a part in relation to a whole.
Few, if any, cities can be neatly compartmentalized in this way. The most prominent enclave may dissipate visually at its periphery. Most urban enclaves lack outstandingly prominent characteristics. Further, complexity in an urban enclave should not be mistaken for confusion. Urban complexity—the intense intermixture of complementary
activities—is one of the major reasons for cities and the spice of urban life. One must also distinguish between uniformity amounting to dullness, and unifying architectural and landscape elements. constituting visual cohesiveness, especially in the face of great variety. We should search for answers to the following;

Components: What are the principal component districts of the city? Where do they begin and end? What are their characteristics, physically and as defined by activity? How apparent are they?
Size: What is the size of a district—its shape, density, texture, landmarks, space?
Appearance: Regarding their physical appearance, what are the characteristics of building forms, building density, signs, materials, greenery, topography, route-pattern landmarks? What is the nature of the mixture of different building types?
Activity: Regarding visible activity, what are the principal clues of the activity of an area—the kinds of people, when and how they move about? What are the key visual elements—the things principally seen—which establish the character of a district?
Threats: What are the threats to a district? What external elements, such as a through road, threaten the health and survival of district? How is the district changing? Is it changing its position? Is an edge decaying? Is an edge advancing, perhaps into a peripheral district?
Emergence: Are there latent districts struggling to emerge, such as a new in-town residential section?
Relation: How do all these parts relate to each other and especially to the route patterns of the entire city? Finally, what are the areas in a city that cannot be classified easily, that lack cohesion in form and character? Are some of these targets for urban design work?
 The Anatomy of a District
Having distinguished the separate parts of the city, it remains to go one step further and survey the parts individually—to diagnose the districts, the parts which constitute the whole. In surveying the visual aspects of a district or enclave we should be asking:
Form: What is the physical form of the place—form and structure in three dimensions and in broad outline? What is the density and character of the buildings? What is the spacing of the buildings? How does it vary? What is the greenery of the place? How would you describe the paving, the signs, the night lighting? How uniform or how varied is the whole, or sections of it? Can a district be further dissected into meaningful places within it? What are these places like? What are the physical patterns of the place? What are the patterns and the linear and focal points or urban spaces within the district?
Activity: What do people do there? How well does architecture and the district serve people? What are the natural groupings of different activities within the district? How does the activity pattern change according to the time of day, week, or season? How lively are the central city areas? How does the local climate affect life in the areas? What are the detrimental aspects of the place?
Features: What are the features of the district—the major hubs or nodes, landmarks, and vistas? What are the major magnets, generators, and feeders? In a busy center-city area, what are the oases, the places of repose? In a quiet residential section, what are the hubs, the places of community focus?
Paths: What are the principal paths of movement in a district? How are they differentiated? How well do they serve the people there? How well do they connect to the larger network of paths? Are the actual physical dimensions of the paths adequate or excessive? How do they determine the physical limits of the districts?
Centers: What are the features of a district that serve a symbolic civic role? What are these places like? Are they lively or lifeless? How can they be made lively? Are they integral parts of the areas around them? Are they part of the life of the community, or are they inanimate symbols?
Intrusions: What are the intrusions and detrimental features of a district? What are the blighting features? Here again one must be careful to distinguish between enlivening intermixtures and truly harmful elements. How much traffic can be tolerated on a street before it is impaired? How little before it is dead?
Change: How is the district changing, both in internal character and the adjustment of its periphery to change? Is there a direction of growth? In which direction is the center of gravity moving? Is the edge decaying? How can a decaying edge be invigorated? How can a district be stabilized?
Improvement: Finally, how can the formation of a new district be aided? What are the new elements of the city that are struggling to emerge? Which marginal districts can be protected and improved as part of the complementary complexity of the whole city? How would you analyze and depict the important districts in your city? What strengths do you discern, what weaknesses? What differences do you find between districts? Is there significance in their relative positions and character?



Activity Structure
An examination of districts and nodes reveals that there are certain spots in the city that have characteristic functions. Generally speaking, these districts fall into such categories as places of living, working, shopping, traveling, leisure, recreation, and learning. There is a logic to the location of these activities and there are definite visual results in their deployment and interrelationships. Density, topography, and transportation routes all affect an urban activity structure.
For example, a high-density residential area will have a central shopping cluster which many of its clients can reach on foot. A low density residential area will more likely be served by a shopping center reached by automobile, its use shared with other lowdensity areas. Topography can dictate the location of routes and therefore the location of centers and subcenters. Topography can also dictate the location of hospitals and airports.
New transportation patterns can alter an existing urban structure by causing the relocation of facilities which depend on a high degree of public access. Shopping centers on a city’s periphery are in large measure a consequence of circumferential expressways. Small neighborhood shopping centers on radial routes are approximate indicators of the centers of residential districts.
A large-scale study of activity structure will reveal the general centers of work and residence and a physical correspondence between activity and district. When tied into an examination of major routes of movement, the relation between activity and circulation access becomes clear. So do points of conflict and areas in transition.
Orientation
If there is logic in the arrangement of a city’s anatomy and if that arrangement is visibly evident—articulated—the sense of orientation will be strong. If there is logic but little or no visible articulation, a city can be confusing even to the point where it arouses a high degree of frustration and anxiety, and the feeling of being lost. Landmarks are a prime aid to orientation, On the overall scale of the city, prominent landmarks are tall verticals like central skyscraper groups, natural features such as rivers or shores, district edges, unique vistas, clear routes which lead to and from a known place, and districts with strong visual characteristics.
Orientation studies should be made on the scale of the whole metropolis as well as small enclaves such as shopping areas, commercial areas, or institutional groupings. Design programs to improve the sense of orientation are particularly important where there are many visitors, as at an airport, or downtown, or at a shopping center. The logic of arrangement and its visible evidence, achieved through design, is the prime device for improving orientation. Signs are a secondary device. Where signs are relied on too heavily, they may add to the confusion or go unheeded.
Orientation studies can be made by the urban design surveyor himself if he is unfamiliar with the area, but they are best made by an interview-map technique.



Details

The appearance of small details, such as cracks in the pavement, parking meters, tree trunks, doorways, are major factors that characterize an area. They tell us of the area’s age, purpose, upkeep, or decay. Signs are an important urban detail. A visual survey should examine the types of signs in an area: for advertising a product; for giving directions; and for marking a building, shop, theater, or hotel. It is important to ascertain the intended audience of a particular sign. If the signs in a shopping area—store names, goods on sale, etc.—are scaled entirely to the pedestrian shopper, they will usually be appropriate. The signs on a highway should be designed for the fast-moving automobilist. On an expressway, signs other than traffic signs may be confusing, especially when seen together with traffic signs. The signs in a busy commercial area that relate to driving should be designed to be readily seen and to give information quickly and clearly. Confusion with signs arises when an area has too many conflicting uses. The solution to these conflicts lies not so much in trying to control the signs as it does in removing the reasons for their mixture.
A visual survey of urban details should, therefore, include sign studies.
More broadly, it includes the quality and conditions of park benches, wastebaskets, streetlamps, pavements, curbs, trees, fences, doorways, shopwindows, etc.—the street furniture and hardware of the city.
Pedestrian Areas
A large part of the difficulty in our cities arises because we have neglected the pedestrian. Walking will always remain a prime mode of transportation. Some areas of the city depend on it almost entirely as a means of communication and intermovement. Many new shopping centers and college campuses are models of design for pedestrian circulation. Older areas in the city need similar treatment. We must be careful, however, in concluding that all the trouble comes from the mixture of pedestrians and cars. Many city streets would be lifeless without cars. The problem comes when cars prevent the free flow of pedestrians. It is possible to have both—cars and pedestrians—in busy urban centers if the cars operate at very low speeds and if through traffic is reduced to the utmost.
A good way to check the quality of pedestrian movement in a busy area is first of all to examine the sidewalks for their adequacy— width, paving, condition, protection from rain and hot sun, and sidewalk outfittings such as benches. Second, one should walk through a pedestrian area taking several different paths to locate the main points of interrupted movement, generally speaking the intersections and crossovers. Too many intersections in city centers are designed to allow a maximum flow of traffic and to subjugate the pedestrian to long and annoying waiting periods. An answer to this problem is pedestrian safety islands and reduced-speed traffic, Pedestrian crossings should be frequent and convenient. A shopping street which is difficult to cross cuts the pedestrian-shop contact in half. The ideal answer to this problem is the separation of cars and people onto different levels, the cars below and the people above. But this is impossible in most cities. In smaller towns it is possible to make the downtown area a pedestrian-oriented zone by providing a convenient bypass road for through traffic and by providing adequate parking garages around the downtown area itself. The essential approach to this problem lies in regarding a downtown area, or any center for that matter, as a stopping place and not a place for through traffic. In outlying areas the same principles of pedestrian flow can be studied, to examine the pedestrian linkages between neighborhoods and their centers. Children should not have to cross busy streets, and the centers themselves should be at the center of a convenient walking as well as auto-shopping radius.



Vista and Skyline
Every city has a few striking vistas—of it and from it. Approaching Dallas, Texas, from the west, one sees a towering cluster of skyscrapers rising from the plains. The approach to Chicago along Lake Shore Drive is a dramatic urban entrance, as is the approach to New York City from the West Side Highway, and Salt Lake City through a pass in the Rockies. These are the major vistas of the city, and they must be protected from intrusion. From the city, too, there are always a few dramatic outlooking vistas. Sometimes these vistas are modest, but still of great importance in characterizing the city. The slot views down the sloping streets of San Francisco afford fine vistas of the bay. Similar slot views down the side streets of Richmond, Virginia, afford glimpses of the surrounding countryside across the river. The views into and out of a city are precious assets. They are an important part of an urban design plan. Some views of the city are in need of legal protection, like the shores of the Potomac across from Mount Vernon. Other views can be complemented by well-poised pieces of architecture, like the buildings of West Point on the palisades of the Hudson River. An urban design survey should note the major views of the city and different points around the city, particularly points of approach. It should also note the major aspects of vista out of the city from points within. Evaluations should be made of improvements needed in both types of vista.
A further study can be made of a city’s skyline. The city’s skyline is a physical representation of its facts of life. But a skyline is also a potential work of art. An urban skyline is its collective vista. It is often the single visual phenomenon which embraces the maximum amount of urban form. Every building that alters the urban skyline should be studied for its effects on the overall view. Many skylines can be improved, particularly by adding a small counterpoint tower at an outlying location. It is interesting to compare the visual effect of a cluster of towers with a single tower. A prominent single tower must be designed as a chef d’oeuvre if it is to be admired. It is too much on display to be mediocre. However, a cluster of towers, like a group of statues, can tolerate less distinguished design, If a tower is to be built at a prominent outlying location, it may be helpful to consider double or triple towers rather than a single shaft. Twins or triplets can be more modestly designed, and their profile as an ensemble can then be more assertive than the single shaft. On the other hand, an elegant profile may be easier to achieve with the single shaft.

Another aspect of vista and skyline is night lighting. Few cities are more dramatic as overall views than when seen at night. Twilight heightens the experience for it adds the drama of sunset to the unified view of the three-dimensional forms of the city. Colored beacons and the shafts of searchlights accent the scene with dots and thrusting lines. A new tower, particularly if it stands alone, should be studied from this aspect of appearance. The buildings of central Detroit are interesting examples of just such studies. The night scene of the city, particularly its lights, is to a large extent within the control of the public. Every city that is building urban highways has a fine opportunity to add a ribbon of unifying illumination to the city’s general appearance. The island of Manhattan is one of the most interesting cities to study from this point of view.
Manhattan can be seen on its two long sides and from the south across large expanses of water. It can be seen as a whole composition of masses and lights. At night the highways that ring the city are marked out by their evenly spaced and specially hued dots of highway lighting—ribbons of dotlike lights against a splash of electric stars. Further, Manhattan’s several suspension bridges now have their catenary cables strung with lights. On a clear night several bridges can be seen simultaneously. The random lights, the even ribbons, and the gracefully curved bridge lights are one of the wondrous urban sights of the world. This illumination theme could well be used as a model in principle for every city. A visual survey of a city at night could suggest just when and how new lights could be added to achieve a similar composition,


Nonphysical Aspects
There are many nonarchitectural aspects of urban character: the New Year’s Day parade in Philadelphia, the Rose Bowl parade in Los Angeles, Mardi Gras in New Orleans. These are a very large part of the image of a city and a large part of its personality. Architects can do much to improve the appearance and urban quality of cities by recognizing them and making better provision for them. Every city has a history, linking it to its origin, and present in the minds of its population. Visible signs of that history can constitute a major aspect of its appearance. Architectural provision can be made for public ceremonies and events, In new areas the inclusion of some visible symbols of the old city’s personality give continuity and character to the new. Every city has a particular purpose which should be expressed architecturally. Boston is a center of learning as well as commerce. New York is a center of culture as well as finance. Miami is a center of leisure. Pittsburgh is a center of steel production. Detroit is our automobile manufacturing center.

Problem Areas
As a result of the visual survey, it is helpful to map the problem areas of a city alone. This map would stand as the urban design diagnosis of ills. It would show points of conflict between pedestrians and autotmobiles, areas with little or no sense of orientation, nondescript or gray areas, ugliness, communities lacking form and definition, areas with confusing signs, confusing circulation elements, incomplete routes, marred vistas, etc. As a diagnosis of ills, such a map would be a direct source of ideas for action programs.

Some Personal Techniques for Surveying
Anyone who attempts a visual survey of his city will undoubtedly develop his own technique and, very likely, a personal vocabulary, In our discussion of this subject we mean primarily to suggest the many different aspects of form that can be examined. But it is also important to be able to link all of the separate aspects of form into a chain of related aspects. One observer, therefore, might want to assemble his vocabulary of form elements into a coherent whole, such as the following: Paths, landmarks, nodes, districts, and edges are the skeletal elements of a city form. On that basic framework stand embellishing characteristics which all together constitute the personality of a city.
Suppose that we think of urban form in the following way: A city or town is generally thought of in terms of size—its population and physical extent. Size is closely linked to shape—the physical outline in horizontal plan form and vertical profile or contour. Size and shape are qualified by pattern—the underlying geometry of city form. Size, shape, and pattern are further modified by density—the intensity of use of land by people and buildings. Density is determined by urban texture and grain—the degree of homogeneity or heterogeneity of use by people or buildings.
We can usually identify the parts of a city by their dominant visible activities. Often these activities are complementary, yet sometimes they are conflicting. It is important not to mistake complexity for conflict; complexity is the spice of urban life. The bustling urban centers are magnets of the city. People are the generators which require magnets around which to rally. Feeders are the links and paths which connect the two.
These areas of dominant visible activity exist in sequence as linked accents. The periodic occurrence of accents in sequence is rhythm. The disposition in a sequence has, of course, visible manifestations. Thus, accents in a sequence produce a modulation of visual intensity—varying degrees of richness of visual experience. Our use of the various parts of a city depends upon their degree of accessibility. Demands for accessibility produce channels of flow. Channels of flow vary in intensity, according to the time of day, week, or season, and thereby establish patterns of movement. Patterns of movement help define districts and act as links.
Visible activity, road signs, store signs, building signs, and symbolic objects are messages to us which convey purpose. They are clues to the organization of urban form.
The visual experience of a city is enriched by major vistas—views of large portions and major elements of the city, and of contrasting natural scenery. We are highly conscious of the nature of land surface (generally thought of as topography). We are aware of going up, going down, and the quality of the surface upon which we move. Natural landscape features form important borders or edges in cities.
Buildings are the immobile masses of a city. Arrangements of buildings form patterns of mass. Arrangements of buildings also form urban spaces which exist as patterns of channels and reservoirs.
Entrances to a city can be accented by portals, the doorways to a city or a district in it. Pauses or relaxations in an intense area are oases—places inducing repose. They are passive accents which complement intense activity. Districts in a city are characterized by a pervading continuity of use, purpose, and appearance, Some districts are oriented to particular types of people or particular age groups. A fine distinction can even be made between masculine and feminine districts.
Our knowledge of these visible phenomena, the presence of visible landmarks, pattern, shape, etc., imparts a sense of orientation— a sense of where we are and where things are in relation to us. A sense of orientation is basic to our understanding, familiarity, and well-being in a city. We are conscious of the age of a city and its parts, the newness and oldness in buildings and places. We must avoid the danger of equating oldness with decay, or newness with amenity. In his work, the urban designer must transcend time and relate all parts of the city to each other. A major objective of urban design is to relate different kinds of buildings, regardless of differences in architectural style, age, or use.

Recording the Results
Visual surveys are most readily recorded as simple maps accompanied by sketches, photographs, and brief notes. The maps can be base maps of the city, at the scale or scales of the survey. The sketches, photographs, and notes can be attached to the maps and the whole study put on display or published as a report, The maps and their notations are best done in a cartoon style and notations of certain features best indicated as a graphic symbol.
Routes of movement can be indicated by arrows, parking garages as a spiral, landmarks as large X’s, vistas as sector lines, points of conflict in red, “gray areas” in gray, etc. One map should show the sum total of the general form of the city and its features. The remaining maps should complement this as a series of detailed aspects of the city’s form.



A full set of survey maps might include the following:
1. Topography
2. Microclimate—sun, wind, and storm directions
3. Shape
4. Patterns, textures, and grains
5. Routes
6. Districts
7. Landmarks and nodes
8. Open spaces
9. Vistas
10. Magnets, generators, and linkages
11. Special activity centers and overall activity structure
12. Hubs of intense visual experience
13. Strong and weak areas of orientation
14. Sign areas
15. Points of conflict
16. Historic or special districts
17. Community structure
18. Areas for preservation, moderate remodeling, and complete overhaul
19. Places needing clarifying design elements
20. Sketch maps produced by the “man on the street” to discern the urban features and forms prominent in the public’s eye.
Each of these maps should be illustrated by a few salient sketches or photos that show exactly what a map symbol represents and also a series of pictures which characterize the area.

Conclusion
Music can be described and discussed with considerable precision and insight because it has a vocabulary and a body of literature. At present painting also enjoys this advantage. So does architecture, to an extent. Up to now the complex modern city has lacked a precise vocabulary for discussing its form and appearance. If we formulate such a vocabulary we will be able to discuss urban form with clarity,
We will also be able to discuss the effects of various actions and policies that affect the city in terms of its buildings, parks, streets, and places. Therefore we will be better able to discuss its design. While developing this language and engaging in conversations on urban form, we must avoid overly abstract terms. Unlike the complexities of modern music or painting, the city is familiar to everyone and can always be described in simple terms. That may be the best test of any vocabulary.



Robert Regis
Summary
The Piazza di Spagna and the Scala di Spagna (Spanish Steps) are among the few and truly unique examples in urban design where stairs, by themselves, serve as a visual and spatial focal center. The sequence of space one experiences in this Late Baroque piazza and stairway (1721–25) by Alessandro Specchi and Francesco dé Santis,
with its 137 steps, is a significant city space in central Rome. The sketchbook—using visual notation and drawing to explore formal, spatial relationships, details and activity of urban places—provides the urban designer a method of observation, documentation and understanding.
Key words

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