Spatial Capital: A proposal for an extension of space syntax into a more general urban morphology

Journal of Space Syntax, vol. 1, nr 1, 2010

Lars Marcus

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Keywords: analytical theory, urban form, accessibility, density, diversity, performativity

Abstract

Although space syntax is often presented as a configurational theory of architecture, this tends to hide

the more fundamental claim that it is also an analytical theory, a theory based on analytical science

rather than on the normative or ideological claims normally found in architectural theory. This article

proposes an extension of such an analytical theory in the context of urbanism by using space syntax

areas in urban morphology that earlier have not been directly part of space syntax analysis. If one

allows for some simplification, one can say that the main variable of urban form analysed in space

syntax is accessibility. This article introduces two other variables: density and diversity. Density, the

dominating variable in geographic analysis of urban space, is fundamental for the development of

knowledge about urban space and in the practice of urban planning. Diversity, at least since Jane

Jacob's writing of The Death and Life of Great American Cities, has been another focus for urban

analysis and urban planners, yet one that has proven to be more difficult to address.

         A study of an urban area in Stockholm identified three convincing correlations: 1.) a correlation

between integration and movement; 2.) a correlation between accessible building density and population;

and 3.) a correlation between accessible plots and diversity indices such as number of age

groups and lines of businesses. Whereas the first correlation is not very surprising in the context of

space syntax research and the second correlation is interesting mostly because of its original measuring

technique, the third correlation must be considered surprising and an original finding.

         The present study proposes that the three ways to measure the three variables accessibility, density

and diversity could be combined into a more general analytical theory of urban form, directly stemming

from space syntax analysis, significantly widening the scope of space syntax into a more general

urban morphology. In addition, it is proposed that these measurements capture something that

can be called spatial capital, that also can engage adjacent scientific disciplines.

1. Introduction: space syntax as an analytical theory of architecture

Space syntax is often presented as a configurational theory of architecture; that is, it specifically deals

with 'the relations of parts in architecture rather than the parts themselves'. This tends to hide the more

fundamental claim that it also is an analytical theory rather than an ideologically founded or normative

theory, as so much of architectural theory - but a scientifically founded theory. As such, it can be

seen as an answer to Françoise Choay's critical investigation that identifies theories in urbanism as inherently normative theories disguised in scientific rhetoric (1997). Similarly, Bill Hillier critiques

the scientific posture of theories in urbanism (1996). By placing his critique of theories in urbanism in

relation to the practice of urban planning and design, he also emphasises the practical problems of

such theories. In short, he puts forth the quite alarming conclusion that we are rich in theoretical

support for the generation of urban designs, but poor in well-founded support for the prediction of the

actual performance of such designs. A conclusion well supported by the fact that so much of urban

planning and design in the 20th century failed to deliver on its claims.

         This article proposes an extension of space syntax as an analytical theory in urbanism and

tries to incorporate into its field areas in urban morphology that earlier have not been directly part of

space syntax analysis. If one allows for some simplification, one can say that the main variable of

urban form that is analysed within space syntax is accessibility: how the accessibility between spaces

in a spatial system varies according to changes in the configuration of urban form. This article introduces

two other variables: density and diversity. Density, the dominating variable in geographic analysis

of urban space, is fundamental in the development of knowledge about urban space and in the practice

of urban planning. Diversity, at least since Jane Jacob's writing of The Death and Life of Great

American Cities (1961), has been another focus of urban analysis and urban planners, yet one that has

proven more difficult to address.

         In addition, this article extends such an analytical theory not by simply adding other measurements

or types of analysis, but rather by using and developing traditional space syntax analysis in

an imaginative way. Perhaps the most important reason for such an approach lies in the unique ability

of space syntax analysis to combine the structural component with the phenomenological component

of urban space in a joint analytical mode, which, using the concepts of Jürgen Habermas, opens the

possibility to move between the perspectives of the system and the lifeworld (1984).[1]

         This article comprises two parts. In the first part, findings from a study of an urban area in

Stockholm are presented that show that through the application of developed techniques of space

syntax analysis one can find strong correlations between urban form and indices of both accessibility

and density as well as diversity. In the second part, it is discussed how this could form an outline of an

extended analytical theory, specifically aiming at the social performativity of urban form, directly

stemming from space syntax analysis while also significantly widening the scope of space syntax into

a more general urban morphology.

2. Urbanity as accessible diversity

On the most general level, an analytical theory on the social performativity of urban form addresses

the relation between urban form and urban life and how these two can be said to generate a sociospatial

category that we call urbanity. Put more distinctly, it addresses how urban form, as a result of

urban design, influences urban life: how it supports, hinders, and organises urban form, creating potentials for variations of urbanity. In addition, this article argues that urban form creates some¬thing

that can be called spatial capital and that this can be measured, providing researchers and urban

planners a new way to evaluate the efficacy of urban planning as it relates to social performativity.

What we need as a point of departure is an appropriate and powerful definition of urbanity

by which we can discern the variables of urban form that will be particularly influential. It follows

that we are looking for a definition on a generic level so as not to get caught in particularities. The

singular most common concept in such definitions is the earlier mentioned density measure - e.g.,

density of population or density of building mass. Still, the concept of density is problematic. First, it

conveys many technical problems of description constantly debated in geography (e.g. O'Sullivan

and Unwin, 2003). Second, density in itself is far from an adequate description of urban form, especially

on the experiential scale fundamental for urban design. For example, high density can be achieved

both in traditional inner-city grids as well as in large modernistic housing estates, but the impact on

urban life in the two cases differs dramatically. From an experiential point of view, it can be argued

that what really matters is the degree of accessibility to density, which is achieved by design of the

urban fabric of streets and buildings - urban form. Degree of accessibility seems to be a vital complementary

variable to density.

         Even so, high density does not in itself necessarily capture urbanity, even when easily accessed.

For example, many institutional areas such as hospitals can be both dense and accessible, but

we do not regard them as typically urban, other than in a derived sense. There seems to be one more

variable necessary to capture a distinctive feature of urbanity, and that variable is proposed to be

diversity. As a matter of fact, it could be argued from a heuristic point of view that the two variables

of accessibility and diversity often over-ride the impact of the more common variable of density when

it comes to discerning urbanity; for example, many small cities with low density present a high accessibility

and diversity and thereby also a strong sense of urbanity.

         Therefore, the generic definition of urbanity proposed here is as follows: urbanity, both

socially and spatially, primarily is constituted by high accessibility and high diversity. We live in

cities so that we can get close to many different things.[2] This is not saying that density is unimportant;

it is proposing that the two concepts of accessibility and diversity are more poignant descriptions of

urbanity. According to the theory of spatial capital, urban form generates variations in spatial accessibility

and diversity with direct effects on social accessibility and diversity, which are possible to

measure, whereby, in turn, it is possible to measure variations in urbanity as a socio-spatial category.

3. Spatial accessibility and how to measure it

The next step is to find analytical means that can capture and measure aspects of urban form that

directly relate to its social performativity and have a powerful influence on the degree of accessibility

and diversity for urban life.

         The most developed technique for such analysis when it comes to accessibility on the detailed

scale we are discussing here is, beyond doubt, spatial integration analysis developed in space

syntax research. Instru¬mental for such analysis is the invention of the axial map, which is a representation

of urban space as structured by urban form and from the point of view of an experiencing and

acting human being. In the map, each axial line represents an urban space that is possible to both

visually and physically access (Figure 1). In short, such analyses measure the accessibility of each

and every axial line from each and every other axial line in the map, the integration value of each line.

Such analyses have proven, in a long series of studies from around the world, that there is a strong

correlation between such integration values and pedestrian movement, the most generic aspect of

urban life (e.g. Hillier, et al., 1993). For example, in the urban areas in Stockholm studied for this

article spatial integration (radius=n) correlated with observed pedestrian movement by 70% (R2=0.70)

(Figure 2).

         Using this technique to measure integration value, other studies have found other correlations

where move¬ment is the intermediary, such as social segregation (Vaughan, et al., 2005), crime

(Hillier and Xu, 2004) and rent-levels for floor-space (DeSyllas, 2000).

Figure 1. Urban space as structured and shaped by urban form in a city district in Stockholm (left) and the axial map of the same area (right).

Figure 2. The distribution of spatial integration, correlating in this case with observed pedestrian movement by 70% (R2=0.70)

In space syntax research, accessibility measure has been further developed into place syntax-analysis

(Ståhle, et al., 2006). Integration analysis, as well as space syntax research in general, deals with the

analysis of urban space per se: what is analysed is the accessibility to urban space in itself without

any regard for the 'content' of space, such as residential population, retail or bus-stops. There is an

important point to this approach, since the differentiation of space as a system in itself, apart from its

'content', is seldom done with any consistency in urban analysis. At the same time, what we often look

for in urban analysis is accessibility to particular contents in urban space such as the ones mentioned

above. In place syntax analysis, the axial map is used as a way to measure distance to such contents,

loaded as place-data on, for example, plots or address-points. It is not only possible to analyse the

accessibility to other spaces, but also the accessibility to specific contents in space. Place syntax

analysis can be said to deal with specific spatial accessibility, such as accessibility to different attractions,

while integration analysis deals with general spatial accessibility, such as accessibility to urban

space in itself.

         Returning to the issue of density, place syntax analysis thus presents a new and in many

respects more life-like mode for representing geographical data. While traditional geographic descriptions

usually deal with representations of such data as density within geographical units (such as

city-districts, blocks or plots), place syntax deals with representations of the accessibility within a

certain radius (such as walking distance) to such data (Figure 3). We can then produce maps showing

'accessibility to density', refocusing on density through the lens of accessibility.

         In the urban area studied for this article, we found a correlation of 82% (R2=0.82) between

accessible building density and accessible population density, a finding that confirms the rather obvious

correlation between high building density and high population density. More importantly, this

correlation was done using measurements that change the perspective from a traditional system perspective,

typical for conventional geographic descriptions, to the perspective of the experiencing

subject in urban space, what can be called a lifeworld perspective.[3] In addition, this correlation was

done using a measurement that brings the ubiquitous density description into the descriptive methodology

developed in space syntax research.

Figure 3. Building density per plot (left), and accessible building density per plot (right), where the latter correlates to accessible population density by 82% (R2=0.82).

4. Spatial diversity and how to measure it

Since the variable of diversity has no analytical techniques as sophisticated as integration analysis, it

is proposed that we need to shift focus from experientially defined space, such as the axial line, to

legally defined space, such as the privately and publicly owned domains we call plots or properties

(Figure 4).[4] The plot, through its disposer, represents the presence of an actor in urban space and the

location of the influence of that actor. Such actors normally develop particular strategies for their

domains. An area with comparatively many plots then seems to have the potential to carry a higher

amount of such actors and thereby a higher amount of strategies for action; in turn, it seems likely that

this would produce a larger amount of diversity among these strategies. In the end, such an area seems

to carry the potential to more easily develop a diverse content than an area with comparatively few

plots and hence few actors and strategies. Obviously, other things like land use regulations can override

the effect of this, but what is tried to be captured here is the particular influence of urban form in

itself.

         Here again place syntax-analysis can be used; this time not to measure the accessibility to

different contents in urban space, but to measure the accessibility to specific types of space in urban

space, such as plots or address-points. For example, one can measure the accessibility to plots within

a radius of three axial lines from each plot in an area, which, following the argument above, could

show the distribution of potential diversity in that area. Still, the measure would be heavily influenced

by local accessibility, since the size of a radius of three axial lines significantly varies depending on

the length of the lines. This effect can be normalized in one of two ways: either by dividing each such

measurement with the accessible plot area within the same radius or by setting the radius to three

axial lines but not more than 500 metres. Such measurements are referred to as measurements of

spatial capacity.[5]

Figure 4. Experientially defined space, where each axial line represents a space that is visually and physically accessible (left), and legally defined space, where each plot represents a domain of an actor defined by legal restrictions (right).

When this technique was tested, what in effect was measured was the accessibility to plots

from each plot within three axial lines, divided by the amount of accessible plot area within the same

radius. These measurements were then correlated to the accessibility to both economic and social

indices of diversity, where the economical index in this case was lines of businesses and the social

index was age groups. It turned out that spatial capacity correlated to 40% with the economical index

(R2=0.40) and to 69% with the social index (R2=0.69),[6] implying that the higher spatial capacity

within a radius from a plot (i.e., the more lines of businesses and age groups within the same radius),

the higher diversity.

5. Conclusion: Spatial Capital - a measurement of urbanity

We can then see how integration analysis and place syntax analysis present powerful techniques for

the analysis of spatial accessibility and diversity as well as an original way of measuring density,

showing how urban form is most influential on generic aspects of urban life.

Figure 5. The distribution of spatial capacity, measured as accessible density of plots (top), correlating with accessible density of lines of businesses by 40% (bottom left) and accessible density of age groups by 69% (bottom right).

Spatial capital, measured by spatial integration and spatial capacity, then constitute a procedure

to measure urbanity that could be both clarifying and useful in urban design as well as urban

analysis. It is important to say right a way that such a measurement does imply that the higher accessibility

and diversity the higher spatial capital, but it does not imply that a higher spatial capital is

always better. In urban design, it is rather a measurement that is able to tell whether certain design

solutions will create greater potential for spatial accessibility and/or diversity or not, where the appropriate

level for this can only be judged in relation to the design task at hand. That is, it can work as a

most important design support but not as a design director.

Figure 6. The variations of urbanity according to the definition of spatial capital as accessible diversity, where spatial diversity is measured as the amount of accessible plots within a radius of three axial lines (top), and spatial integration and capacity overlaid in one map, showing the continuous variations of spatial capital (bottom).

In urban analysis, it can be useful both as a straight description of the variations of spatial

capital in an urban area or as descriptions of spatial accessibility and diversity separately (Figure 6).

The latter case, for example, presents the interesting opportunity to discern urban sub-categories.

There is an abundance of taxonomies and typologies used in the discourses of urbanism, the transects

in New Urbanism being just one. There are good reasons for that since categories and types simplify

communication. The problem is that such typologies often have weak ties to urban life, which make

them isolated and rather uninformative typologies of urban form per se. The theory of spatial capital,

on the other hand, presents the opportunity to discern such categories or types with an unusually

strong analytical foundation, where urban form is tied to generic aspects of urban life, constructing

genuine socio-spatial sub-categories of urbanity. From such a description, four fundamental urban

categories can be suggested (Table 1) although there are no implied values to the different categories.

Once again, returning to density, it is obvious how the table could be extended by the addition of a

high- and low-density type for each category.

6. Discussion: Spatial Capital as exchange-value and use-value

Recently, the concept of capital has been intensely discussed and extended; according to Pierre Bourdieu

(1986), for example, in addition to economical capital there are cultural capital and social capital.

The more precise meanings, according to economist Hernando de Soto, are often forgotten even

when it comes to economical capital. In his book The Mystery of Capital (2000), he thoroughly

discusses how a certain value can be translated into capital, which is of more general interest than his

specific propositions in the same book on how to solve world poverty, claims that are clearly more

debatable.[7] His main example is land and how land becomes capital, the question being trickier than

it first looks, according to De Soto. After land, or rather different land parcels, are geographically

defined and their particular social and economic values described, measured, and documented to

represent the land parcels, these documents need to be authorised and integrated in a legal system

where such things as ownership and economical transactions are controlled and guaranteed.

Table 1. Four sub-categories of urbanity and suggestions for ideal cases discerned through the theory of spatial capital. overlaid in one map, showing the continuous variations of spatial capital (right).

In this context, the concept of spatial capital may contribute to the possibility to measure the

effects of urban form on land-value. We all agree that different locations in cities have different

economic values, which influence such things as property prices and rents. And even though markets

react on exactly such values and there is a whole industry trying to analyse them, the specifically

spatial preconditions are difficult to capture, especially on the detailed scale we are referring to here.

The analytical techniques above then seem most interesting as a means to develop more precise tools

for such evaluations, especially when it comes to predicting how new urban projects will create new location-values as well as redistribute already present ones. Obviously, there are other values at work here, such as the value of what is actually built, but the theory of spatial capital specifically aims at the evasive value of urban form.

         This concerns the exchange-value of spatial capital, suggesting how the value of urban form literally can be translated into economical capital. But just as important is the use-value of spatial capital, the value urban form represents in a multitude of ways for everyday urban life - socially, culturally, and environmentally. Although not all needs require high spatial capital, on the most fundamental level this seems to be what cities offer: the support of the generic need for people and societies to access differences as a means for social, cultural, and economic development. In the end, we here seem to see the major reason behind the accelerating growth of our cities - for people poor in economic, social, or cultural capital, cities offer spatial capital, for people rich in economic, social, or cultural capital, spatial capital enhances its value.

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Notes

[1] This aspect is discussed at depth in Ståhle et al. (2006).

[2] In this regard cities can be said to be very similar to the internet, and both can maybe be seen as successful answers to the same fundamental need.

[3] A full discussion on this is found in Ståhle et al. (2006).

[4] For a full theoretical discussion on this shift in type of space, see Marcus (2000).

[5] The concept of capacity is similar to the concept of capacity in computer science, the ability to carry differences.

[6] It is important to stress that the population that is correlated here consist of no less than 1700 plots, encompassing a complete inner-city district including some pure residential areas. Against that background, the correlation for the economical index is surprisingly high rather than low. Furthermore, by excluding 17 out of these 1700 items, the correlation rises to R2=0.60, which tell us that the correlation is fundamentally strong. Further and more detailed investigations on these promising correlations are currently under hand.

[7] See, for example, the critique put forth by Mike Davis (2006).