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To be cited as: Dovey, K. & Pafka, E. (2016) 'The Science of Urban Design?'
Urban Design International, 21 (1) 1-10 doi:10.1057/udi.2015.28
THE SCIENCE OF URBAN DESIGN?
Kim Dovey and Elek Pafka
Abstract
In a provocative paper Marshall (2012) suggests that a range of seminal urban design theories
stemming from the 1960s – Jacobs, Alexander, Lynch and Cullen – can be construed as pseudo-
science because they haven't been tested empirically. Adding Sitte and Cerdá, we take this
provocation as a chance to raise some questions about the nature of urban design knowledge,
theory and practice. We suggest that this work is not and cannot be empirical science but is based
in the detailed observation of cities using multiple logics. While there is an emerging science of
cities, urban design knowledge is much broader, spanning both natural and social sciences as well
as the arts and humanities. We also argue that it is a particular form of diagrammatic socio-spatial
knowledge that cannot be reduced to either words or numbers. These thinkers remain seminal
more for the questions they open than the answers they provide.
Introduction
In his paper 'Science, pseudo-science and urban design' Stephen Marshall (2012) argues that a
series of seminal urban design theory texts might be considered pseudo-science in the sense that
they seem to have a testable scientific basis but upon examination they turn out to be untestable or
(where they have been tested) false. In a similar vein Lampugnani (2012) calls for a scientific
foundation for the field of urban design and Batty (2013) celebrates the emergence of a new
science of cities that incorporates urban design. Marshall's paper examines four key texts: Lynch's
'The Image of the City' (Lynch, 1960), Cullen's 'Townscape' (Cullen, 1961), Jacobs' 'The Death
and Life of Great American Cities' (Jacobs, 1961) and Alexander's seminal paper 'A City is Not a
Tree' (Alexander, 1965). We do not contest Marshall's main arguments – that such theory often
appears to make empirical claims, that such claims are often untestable (therefore not science),
and that to the degree that they are testable then they should be tested. We suggest, however, that
some of such testing is itself a form of pseudo-science. Our goal here is to pursue some of the
questions that are opened up, particularly the question of the degree to which urban design theory
can and should be considered a science.
We will deal with this through a critique of the specific sets of ideas and concepts derived from
Lynch, Cullen, Jacobs and Alexander. In order to understand the roots of such urban design theory
we begin with a discussion of two 19
th
century predecessors – Camillo Sitte and Ildefonso Cerdá.
Sitte is widely seen as a precursor of Cullen and Cerdá's theoretical work can be seen to prefigure
that of Jacobs. We cannot cover all the work of these writers here, nor compare them in any detail;
our goal is to raise questions about the nature of urban design knowledge, theory and practice.
How does theory work in a field that ranges from the mathematics of urban morphologies and the
sociology of public space to the interpretation of design quality or aesthetic value? We will suggest
that while there is an emerging and promising science of cities, urban design knowledge is much
broader, that it is a particular form of diagrammatic socio-spatial knowledge that cannot be
reduced to either words or numbers. These seminal texts of the 1960s and earlier are dated in
many ways but they remain valuable for the questions they open as much as the answers they
provide.
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Sitte and Cullen
Sitte was one of the most influential early thinkers who aimed to establish urban design as a
discipline joining art with science. His major book entitled 'City Building According to Artistic
Principles' (1889) had the goal to rescue urban planning from the traffic engineers, to revive an
aesthetic of city planning that geared it to the pleasures of everyday life in public space. Urban
design was a human-centred task, a science as well as an art (Ley, 2007). Sitte's understanding of
art was strongly linked to the study of human perception. Inspired by the writings of Fechner, the
founder of psychophysics, Sitte explored the relationship between urban spatial and human
perception (Wilhelm 2006, p.40). He wanted to extract essential principles of urban design that
run deeper than design style.
A large part of the book is dedicated to the systematic study of contemporary and historic typo-
morphologies of urban squares in Europe. His method resembles that of 18th and19th century
morphological classifications in the natural sciences (Wilhelm, 2006, p.38). While linking
morphologies to visual perception Sitte's main preoccupation is with legibility and the picturesque
cityscape (Collins and Collins 1965, pp.50-51). He was fascinated by perspective and a
conception of urban space as a form of theatre. Sitte's approach involved an implicit critique of
the role of public space in the legitimation of power in that he opposed monumentalist urban
planning that focused on free-standing buildings and monuments. He argued that squares and
plazas should be enclosed with the centre kept free for the life of the city; the size should relate to
that of the surrounding buildings with a reciprocal relation between architecture and public space.
Sitte was also concerned with the smaller street networks and buildings of the city and was
famously opposed to the regular grid in favour of the informal morphologies of medieval street
networks. While these observations have been dismissed as subjective and romantic, they were
argued on the basis of both picturesque effect and the ways the character of urban space was
formed by evolutionary adaptation. While the book's success has been attributed to the clarity of
the writing and diagrammatic maps, Sitte considered its success to be an indication that his
theories resonated with the perceptions of the broader public. The influence of Sitte's work
diminished during the early 20th century when it was misinterpreted as 'medieval romanticism',
based in part on a misleading French translation (Collins and Collins, 1965). From the mid-20th
century a more nuanced reading of his work brought Sitte's morphological and phenomenological
contribution to urban design theory again into attention. Consequently he was seen as a precursor
of a 'critical urbanism' that conceives cities as socio-spatial phenomena (Wilhelm 2006, pp.86-
88).
This mid-20th century interest in Sitte's work was paralleled by Gordon Cullen's Townscape
(1961) (Larice and Macdonald, 2013), and the later German edition of Townscape (Cullen, 1991,
translated by Gerhardt) referred to its author as the "Sitte of the 1960s". While he is best known for
Townscape, Cullen's preoccupation with the visual perception of urban space and the concept of
'serial vision' date back to the articles he had published since 1947 in The Architectural Review
(Gosling, 1996). Cullen's work is avowedly aesthetic rather than scientific: "we have to rid
ourselves of the thought that the excitement and drama that we seek can be born automatically
out of the scientific research and solutions arrived at by the technical man… We naturally accept
these solutions but are not entirely bound by them…" (Cullen 1961: 10). For Cullen the evidence
for urban design quality is the visual experience of the city. By the concept of 'serial vision' Cullen
seeks to understand the complex ways in which urban experience unfolds for the mobile subject,
arguing that a diversity of different forms and spaces experienced over time enriches the emotional
and aesthetic impact of the city. This was particularly focused on differences of openness and
enclosure as one moves through narrow pathways and small public spaces towards grand open
spaces and vistas.
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Rapoport and Kantor's (1967) examination of Cullen's work found it to be congruent with
contemporary research in psychology that showed that humans prefer somewhat structured yet
ambiguous and complex visual environments, rather than entirely monotonous or chaotic ones.
While there have been further attempts to test this in detail based on historical morphological
analysis (Rapoport, 1990) and comparative phenomenological analysis (Isaacs, 2000), the
limitations of such studies are so wide-ranging (sample size, cultural differences, complexity of the
studied phenomena) that the results can only be interpreted as supportive of the theory rather than
scientific proof.
There is also a further problem in that there are clear limits to any science of aesthetics. Suppose
we could prove empirically that people generally prefer certain cityscapes, urban imagery or open
space designs – this won't persuade those who accuse Sitte and Cullen of romanticism because
such critique stems from the humanities and not the sciences. Theories of the picturesque can only
be tested by reducing the city to a picture, and it is this reduction that is at the heart of the critique
of the picturesque (MacArthur, 2007). The attempt to create such streetscape effects through urban
design can easily fall into a production of formularized picturesque scenography.
Lynch
While Lynch’s work on urban design theory is very broad the primary work under discussion here
is that on the image of the city comprised of the set of five elements - nodes, paths, edges, districts
and landmarks (Lynch 1960). In the preface Lynch acknowledges the debt to his mentor Gyorgy
Kepes, who co-directed this research at MIT in the 1950s. Kepes is the painter and art theorist who
argued for a universal ‘Language of Vision’ (Kepes, 1944) and was strongly influenced by German
gestalt psychology. The ‘gestalt’ is a pattern or a whole that emerges as more than the sum of its
parts, where parts and wholes are co-dependent - we don’t simply perceive an objective world,
rather we organize parts to construct wholes (Arnheim, 1954). Lynch's quest is to articulate
universal patterns of experience and perception, based in elements of urban morphology.
Two separate research methods were used by Lynch: a detailed mapping of the subject areas by
trained observers, and in-depth semi-structured interviews with residents (Lynch 1960:
Appendices). Interviewees were asked to identify elements of the city and their boundaries; their
responses were then analysed according to the typology of landmarks, paths, edges, nodes and
districts. This typology appears to be the framework for analysis rather than a finding that emerges
from the interviews; it is a hypothesis that is confirmed by the data. In other words the elements
largely derive from gestalt theory as the wholes that emerge from the parts, figures against the
ground of the urban fabric. Landmarks mark the land, districts are patches of consistent character,
nodes are junctions and crossings of paths, paths are lines of movement and edges are barriers to
movement. This typology has become seminal, not because it was affirmed empirically, but
because it resonates with a gestalt ‘language of vision’ to use Kepes’ phrase, with a universal
practice of urban cognitive mapping.
Conceptually the elements are a mix of centres (landmarks, nodes), lines (paths, edges) and
territories (districts). What unites them is that they are all perceptual wholes that interact to form
the image of the city. They all draw upon gestalt perceptual tendencies to construct identities out
of differences. The question of the degree to which a particular building figures as a landmark in
the image of the city can be tested empirically (if such a fact were valuable) but the question of the
validity of the category of the landmarks as a primary element of urban cognition is of a different
order. The primacy of figures that mark the land and our pathways across it can be deduced from
gestalt theory. Lynch's elements were picked up in practice because they resonate so well with the
urban phenomenology of everyday life – we navigate streets, past intersections and landmarks,
across boundaries and through different neighbourhoods.
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This set of elements, however, is also problematic. The closer one looks the more the boundaries
between ‘elements’ blur and intersect in a manner that dissolves the differences between them. A
node is defined as an intersection of paths and is often also a district. A major path may become a
district or an edge to a district. Some elements become others through the effects of scale, as when
a path at metropolitan scale (freeway) becomes an edge at neighbourhood scale. There is no
objective sense in which this is a complete set of elements. Lynch includes the urban plaza or
enclosed void within the urban fabric as a node (Lynch 1960: 78), however, if the study were
based on European cities there may have been an additional element of the urban void (more than
just the inverse of the landmark). If the analysis were based on Asian cities there may be a different
set again.
Lynch’s theory becomes problematic when the line is crossed from urban design theory to
practice; when we move uncritically from the question of ‘what makes the city legible?’ to ‘how to
make the city legible?’. Legibility is the degree to which spatial orientation within the city is
accessible to outsiders – a legible city will show a stronger correlation of cognitive mapping
between insiders and outsiders. Legibility makes the city easy to learn but it is scarcely an
unmitigated good. Cullen's notion of serial vision celebrates the aesthetic of illegibility, or at least
the joys of discovering the city one street and place at a time. Lynch suggests ‘there is some value
in mystification, labyrinth, or surprise…but only where there is no danger of long-term
disorientation ‘(1960: 5-6). Yet the long-term danger of the quest for legibility, beyond the
boredom of formularized urban design, is that we misrecognize these perceptual wholes as parts;
that we seek to build the legible city out of a kit of parts - paths, nodes, landmarks, districts and
edges – while forgetting that they are the emergent wholes.
There is another key reason why Lynch’s categories are not a form of science. While Lynch
recognizes that one cannot separate urban cognition from questions of meaning, this work barely
scratches that particular surface. While there is no scope here to pursue such questions, urban
landmarks clearly have potency as symbolic and political capital; nodes and districts are sites of
intensive social encounter; and edges are forms of social segregation. These are questions for the
humanities and are rarely empirical questions.
Cerdá
Ildefonso Cerdá is mainly known as the designer of Barcelona's 19th century extension and the
person who coined the term "urbanization". Less known is that between 1855 and 1876 he
produced a vast oeuvre of urban theory that was in part based on systematic socio-spatial surveys,
morphological analysis and observation-based insights into cities that he understood as complex
movement economies with synergistic relations between their components (Soria y Puig, 1999).
Cerdá's explicit intention was to establish a multi-disciplinary science of cities that relied upon
political economy, social science and philosophy among other disciplines (Soria y Puig, 1999,
pp.64-66). This approach attracted broad disapproval from the local elite who considered city
building to belong to the realm of art. This conflict, along with the gradual socio-political
exclusion he was subjected to, is seen as one of the reasons why his work has been buried in
archives for a century (Soria y Puig, 1999, pp.37-40) and as a result remained for so long
inconsequential in the history of urban theory (Choay, 1997). Until today most of his work is only
accessible to Spanish speakers with the exception of fragments included in the anthology by Soria
y Puig (1999).
One of Cerdá's most comprehensive empirical undertakings was a statistical analysis of Barcelona
which then comprised 518 urban blocks with a population of over 190,000. He examined the
correlations between the number of deaths by cholera between 1856 and 1865, their location of
residence (district, city block) and urban form (storey, street orientation and gross block density).
While hygienist theories of the time suggested that mortality by infectious diseases correlate with
density, Cerdá’s study showed a correlation instead with social status. However, only the raw data
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was published and the implicit conclusions of the survey were not made explicit (Soria y Puig,
1999, pp. 270-273). The false association of density with morbidity continued to influence urban
design until its rebuttal in the 1960s and '70s (Mitchell, 1971; Cohen and Sherrod, 1978).
While Cerdá attempted to ground his theory on verifiable empirical evidence, he understood that
cities are made of complex interrelationships between multiple urban elements and that groupings
of elements lead to emergent effects that couldn't be simply explained as the sum of the parts. He
also understood that any change to one element can lead to divergent effects overall (Serratosa,
1999). He meticulously considered the advantages and disadvantages of a large range of urban
forms including street length and width, block shape and size, orientation, intersection
configuration, building coverage and height. Yet when designing he ultimately relied upon
umbrella concepts of egalitarianism and political justice. Many elements of the Barcelona
extension plan such as the regular grid, square blocks, 45 degree orientation to the cardinal points,
uniform street width were a result of the aim to create an urban structure that provided equality of
opportunity without pre-established formal hierarchies. Cerdá wasn't concerned with such an
approach leading to monotony as differentiation would inevitably occur in unregulated aspects of
built form, such as building height, façade design and socio-spatial patterns. While relatively
uniform height limits were imposed by the city council, a review of Barcelona's evolution in the
past century shows diversification of urban form – some blocks are divided by shortcuts, some
courtyards have become public parks or are covered, and there is a diverse functional and social
mix throughout the grid (Barcelona City Council, 2010).
Apart from his investigation of hygienist theories and urban morphology, perhaps the main thesis
in Cerdá's 'general theory' is that streets as connections between people and buildings constitute
the basis of urbanization (Soria y Puig, 1999, p.103). At the larger scale, cities were defined as
nodes "along the universal economy of ways" (Soria y Puig, 1999, p.115) preceding Hillier and
Hanson's (1984) concept of cities as 'movement economies' by over a century. Cerdá's concept of
a synergy between streets, buildings and people was reflected in two further neologisms he
coined: 'viality' that combined street (via) with vitality and 'inteways' that referred to building
blocks being defined by streets. These concepts were not the result of scientific testing, but rather a
result of his observations of the dynamic nature of 19th century cities.
Cerdá's unfinished General Theory of Urbanization (1867) is similar to other 19th century
approaches by individual authors to systematically draw together and connect various fields of
knowledge that can lead to a better understanding of cities. For example in Germany the treatises
of Baumeister (1876) on 'city extensions' and Stübben (1890) on 'city building' are seen as similar
attempts to develop a basis for a scientific approach to urban design (Ley, 2007). Similarly, these
German works haven't been translated, and seem to have had limited impact. In recent years this
led to critiques that parallel Marshall's, of a lack of scientific underpinning of contemporary urban
design theory as well as of the risk of being marginalised by other fields of science (Lampugnani,
2012).
Jacobs
The urban design work of Jacobs is probably the best known of any of these theorists and Marshall
is correct to suggest that much of the literature about this work is superficial and there is little
empirical testing. Her insights are largely based on personal observations of the streets of
Greenwich Village as contrasted with other parts of New York – the uses of sidewalks, place
ballet, eyes on the street, the importance of the public interface all comes from there. The key
ideas that are of concern here are the principles of permeability (short blocks), functional mix,
formal mix (old buildings) and density (concentration) that she argues are necessary conditions for
the good city. This body of theory, with substantial elaborations and a new language, is perhaps
the most robust piece of theory within the field of urban design. But is it scientific and to what
degree might it be tested?