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CUPUM/ECiD Joint Workshop 'Design out of Complexity' - UCL, 2 July 2005

STEPHEN MARSHALLThe Young Foundation

Bartlett School of Planning, UCL

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The Urban Design Agenda

Neo-traditional urbanism now in favour Traditional patterns now seen as models

But these patterns were not planned

How to plan or design these?

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Random

(Mandelbrot)

Chaotic

(Keeble)

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Characteristic Structure

Two senses:

Typical distinctive character

Likely

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Characteristic Structure

Typical distinctive character

Means the quintessential street patternshape

Not like a gridiron

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Characteristic Structure

Typical distinctive character

Means the quintessential street patternshape

Not like a gridiron Not like a tree

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Characteristic Structure

Typical distinctive character

Means the quintessential street patternshape

Not like a gridiron Not like a tree But like nothing otherthan a street pattern

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Characteristic structure

of street patterns

a mixture of short and long routes, and more and less

connective routes; some differentiation of routes by depth, but overall not

too great a depth;

three-way junctions are typically in the majority, butlikelihood of at least some crossroads and culs-de-sac;

a medium or semi-griddy level of connectivity, with arelative connectivity () of around 0.35-0.45;

a relatively high degree of irregularity and complexity,with complexity ()

typically in the range 0.35 to 0.6.

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DESIGN

EVOLUTION

TOP-DOWN

Pattern selection

Patternsgenerated by

programs

BOTTOM-UP

Different kinds of program

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Kit of identical parts

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Kit of identical parts

(i) generation 1

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(i) generation 1

(ii) generation 2

Kit of identical parts

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(i) generation 1

(ii) generation 2

Kit of identical parts

or

(iii) generation 3

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The T-tree program

_|_ _|_ _|_ _|_ _|_ _|_ _|_ _|_

1) Each constituent element is identical.

2) Each element is added to form structure one at atime.

3) Each new element occupies a position on thestructure that is chosen at random.

4) Each new element joins the existing structure atonly one of its ends, to form a 3-way connection (T-junction), such that the overall structure is a T-tree.

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Case Frequency Probability

a 1 4%

b1-6 6 25%

c1-3 3 12.5%

d1-4 4 17%

e1-4 4 17%

f 1 4%

g1-3 3 12.5%

h 1 4%

i 1 4%

Total 24 100%

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More frequent(three variants)

Typicality

Less frequent(each a singular

type)

Comb Irregulars Fractal

Type

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The X-cell program.

1)Each constituent element is identical.

2) Each element is added to form structure one at atime.

3) Each new element occupies a position on thestructure that is chosen at random.

4) Each new element joins the existing structure atone or both of its ends (but not along its middle);the resulting structure can have multi-spoked nodesand form circuits.

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Deeply layered andbranching structures

Meshes and spokes

Long chain structures

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Area whereactual streetpatterns aretypically

found Grid-likestreetpatterns

Inter-mediate

Tree-like

streetpatterns

1.0

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0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

1st, 2nd 3rd generation Real (Figure 8.4)

4th generation 4th gen. resultant

2D

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2D

3D ti t

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3D nesting, etc.

Ziggurat of Ur

I Di t l ti f

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ba2a12a11

a1 a2 b c d e f

I. Direct selection ofwhole pattern single act of design

II. Selection atsuccessivestages in design,directing growth

towards desiredoutcomeProgram e1

e2

III. Selection of programs

Conclusions and Implications

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Conclusions and Implications

1. Demonstration of a possible mechanism for the

probabilistic generation of characteristic urban

structure

Conclusions and Implications

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Conclusions and Implications

1. Demonstration of a possible mechanism for the

probabilistic generation of characteristic urban

structure2. Neo-traditional patterns could be recreated using

programs rather than pattern templates

Conclusions and Implications

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Conclusions and Implications

1. Demonstration of a possible mechanism for the

probabilistic generation of characteristic urban

structure2. Neo-traditional patterns could be recreated using

programs rather than pattern templates

3. A program-based design approach can use simplerules yet generate complex patterns

Conclusions and Implications

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Conclusions and Implications

1. Demonstration of a possible mechanism for the

probabilistic generation of characteristic urban

structure2. Neo-traditional patterns could be recreated using

programs rather than pattern templates

3. A program-based design approach can use simplerules yet generate complex patterns

4. This approach could be an alternative toconventional town planning or master planning

Conclusions and Implications

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Conclusions and Implications

1. Demonstration of a possible mechanism for the

probabilistic generation of characteristic urban

structure2. Neo-traditional patterns could be recreated using

programs rather than pattern templates

3. A program-based design approach can use simplerules yet generate complex patterns

4. This approach could be an alternative toconventional town planning or master planning

5. Possibility of practical application through synthesis

of urban coding + road hierarchy

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S T E P H E N M A R S H A L L

s . m a r s h a l l @ u c l . a c . u k

w w w . s p o n p r e s s . c o m

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CITIESCITIESCITIES

DESIGN &DESIGN &DESIGN &

EVOLUTIONEVOLUTIONEVOLUTION

S T E P H E N M A R S H A L L

s . m a r s h a l l @ u c l . a c . u k

w w w . s p o n p r e s s . c o m