MSc/PgDip/PgCert
Urban Design
2012 / 2013
04
ANALYSIS BRIEF
Experiencing and comparing place
Sergio Porta, Ombretta Romice, and Tutors
In partnership with:
The Prince’s Foundation for Building Community
http://www.princes-foundation.org
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Analysis brief 04: Experiencing and comparing place, 2012/13.
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Introduction
The MSc in Urban Design is articulated into four phases:
1. Case analysis. You students will work in groups on the study area as part of a larger urban
sector, getting to know intimately this area, its links potentials and pitfalls (Studio 1a);
2. Urban Design Strategy. You will propose a Strategic Plan and a Concept Plan, together forming
the Urban Design Strategy, for the improvement of this area envisaging actions and projects that
deal with services, mobility, housing, and public realm provision (Studio 1b);
3. Street front analysis and coding. You will be requested to work out a complete morphological
analysis of two street fronts that are assigned by staff. The “front analysis” is carried out by
drawing each street front in two boards and by the quantitative analysis of morphological aspects
as they appear on drawing. Once all cases have been worked out and all data is available,
students and staff derive from that a synthetic Local Urban Code (Studio 1c).
4. Masterplanning and place design. You are led to the production of a Masterplan for sub-areas of
the study area. You will learn how to take action for subdivision of large blocks, a correct
management of density as related to transport and land use, how to design safe and liveable
streets and how to interpret the existent urban fabric of public and private buildings in relation to
streets, land uses, density and transport. Finally, you will be asked to deepen your Masterplan
and Code by experimentally developing the design of streets and buildings in a small part of it
(Studio 2).
One feature of this course is to strengthen the work on urban analysis by means of analytical “packages”,
each of which will be carried out by one single group of students in the first phase of work, corresponding
to “AB 931 - Urban Design Studio 1a”. In addition, by undertaking “Street front analysis and coding” you
will be led to understanding the structural characteristics of the urban fabrics, their spaces and measures.
The resulting learning experience is this year particularly dense of arguments and different methodologies
will be taught in order to give you basic notions of what are the “tools” that an Urban Designer may apply to
the interpretation and modification of urban spaces. All this results in a very challenging programme, which
is still experimental this year, which will require highly committed students and staff to be successfully
completed. On the other side, this programme is a very unique one, in that it blends operational tools with
community involvement and a strong – even physical – immersion in the local reality, i.e. theory with
hands-on approaches.
Perhaps the most challenging phase of the entire course is the first, the analytical phase. Because all
analysis must be completed in about one month time, and because such analysis are all very demanding,
especially for students who have never approached urban studies before and are requested to work with
mostly new team mates. For these reasons we decided to write these Analysis Briefs.
We have written 5 Analysis Briefs, one for each “package” of analysis, which means one for each group of
students:
1. Drawing the existing city.
2. History and stories
3. Planning framework
4. Experiencing and comparing place
5. Network analysis of streets
These briefs should be considered by all of you a constant reference during the work in phase 1. We have
put into them all possible instructions for the correct completion of every task, with as much detail as we
were able to manage. For the same reason these briefs are fully illustrated, so that at every step you will
have an idea of the sort of thing the final result should look like. Of course, with all their details, these notes
do not set compulsory rules: you are always welcome to do it differently upon a serious discussion of goals
and methods, which we are certainly more than happy to help doing.
This is a way for us to speed up the process of learning by doing. This also witnesses the investment that
we as staff have done on this rather ambitious course, a dramatic bet addressed on the ground of our
highest expectations on you. We recommend all of you to react by mobilizing all your personal, intellectual
and motivational resources, without which there is no one chance to get this course – and your learning
experience with it – actually complete and significant at the end of the year.
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4.1 Scope and objectives
WP1. Experiencing place
Scope:
The broad scope of this Analysis Package is to understand the study area by confronting the subjective
knowledge of the place coming from the inhabitants and your own experience with the more objective
knowledge coming from systematic map comparison. This subjective examination of a place in conjunction
to the more objective comparative study, is fundamental in revealing its actual performance. The work is
therefore split into two distinct work packages (WP).
Analysing into perception of space started in the ’60 – environmental perception is the area of investigation
of a broad field of studiers that since then gathered geographers, architects, urban planners,
psychologists, sociologists. Their main focus was the study of the relationships between people and space.
In general, there is agreement on the fact that the nature of perception of the physical environment is
relative, selective, dynamic and is a function of the stimulus, experiences, interests and needs of the
perceiver. In other words, perception of places varies greatly between people; therefore, to gain a
comprehensive, meaningful understanding of how people see the study area, this group will have to
examine and compare the ‘professional’ perception (of the members of the group itself), and the ‘users’
perception, that is of the people that live and work in it.
There are moreover many aspects to environmental perception, and over the years many useful
techniques and tools have been devised to map it. As part of this Analytical Package, we will ask you to
use a few as described below.
As for all other groups, we are interested in mapping the knowledge gained through the exercises listed
below. You will produce a series of maps which will appear at times very different from those produced by
other groups. Differences and similarities, once brought together, will reveal a great deal on how the study
area works for those who use it.
At the end of the work in this phase, students in this group must be able to answer 5 questions and
illustrate their answers to their fellow classmates. Moreover, they should do that mainly – if not only – by
means of graphic layouts. The five questions are those listed below:
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What is the composite image of the study area that residents and professionals hold and what are
the main differences?
What are the main character areas, how accessible are they and how do they link to each other?
What is the perception of safety throughout the study area?
How legible is the study area as a whole, and what are the features that contribute or undermine
its legibility?
What is the state of maintenance and repair around the study area and are how does it link to
urban types?
Objectives:
1. To generate composite mental maps by students and residents and compare them.
2.
To determine character areas and their salient aspects.
3.
To trace the elements that contribute to create and image of the place and help people navigate
through it.
4.
To represent perceived performance elements such as safety, accessibility and maintenance
throughout the area and link these to urban elements.
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WP2. Comparing place
Scope
Students will investigate the role of the urban fabric in assessing the proper functioning of the city. The
urban fabric is a combined expression of streets and block design. The design of the site layout and in
particular of the urban grid is a powerful tool to control and manage the sustainability of a city. We assume
here, that the urban fabric intended as a structural property is sufficient alone to explain some
characteristics of the city concerning connectivity and accessibility.
The capacity and the arrangement of the street network are key elements in the determination of
accessibility. In this work we refer to the arrangement of the network alone, the so named “topological
accessibility”, since we are interested in analysing those variables that are directly related and controlled
by the work of urban designers.
For instance, both social and environmental aspects are intimately bounded to the design of the urban
fabric. A permeable urban fabric is walkable and gives to people the chance to meet on the public realm.
One of the basic urban design rules informs that the more physical connections we have on the street
network, the more human connections can consequently be promoted.
Connectivity of the street network
Street connectivity is a key component for a good urban design. Highly connected street networks perform
better in terms of sustainable mobility, encouraging walking and bicycling in urban areas. In fact, grid-like
urban structures offer more opportunities for activities and social interactions in general and reduce the
travel demand, since everything is reachable in a shorter time.
The apparent contradiction that having numerous connections on the street network would leads to
congestion can be denied by correct transportation policies, whereby the car is not considered as the
protagonist of travelling and pre-car age models are newly taken into account.
Even if these principles are generally accepted in the urban design community, the question regarding how
to establish the connectivity of a place is very open. Numerous indicators have been developed and
imported in the urban design practice from very different fields, like biology, physics, geography and
sociology. Network analysis and graph analysis collect all this knowledge and represent interdisciplinary
research sectors and their applications are useful in very different domains.
The proposed indicators and tools that follow try to delineate a possible practical answer to connectivity
measurements for the purpose of increasing walking and cycling in the urban planning design process.
These indicators are particularly useful in comparative studies, like for example in cases where we have to
analyse a specific condition before and after intervention.
Accessibility of the urban network
Accessibility is defined as the measure of the capacity of a location to be reached by, or to reach different
locations. Therefore, the capacity and the arrangement of transport infrastructure are key elements in the
determination of accessibility (Rodrigue et al., 2009). A set of structural indicators of connectivity and
accessibility is presented in this section.
Objectives
1. To understand the basic differences between urban fabrics as a result of different street layouts.
2.
To reflect on the historical factors that stay behind the visible manifestations of street layouts.
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4.2 Working instructions
Timetable:
WP1. EXPERIENCING PLACE
1. Kevin Lynch @ the study area (week 1-5):
Visit the site. You will need to familiarise with the site and walk, drive, cycle around it as much as
possible. Use public transports (bus, underground) too, it is important to understand how well the
study area is served. As much as this is something you will do through the year, the first week is
crucial for the following exercises.
Achieve literature. This is very straightforward: all group’s members should read and discuss
within the group Kevin Lynch’s classic work “Image of the City”. They should pay attention to how
mental maps of cities are drawn and become familiar with legends and symbols, taking into
account that they will work out their maps in colour.
The first studies on mental maps were fundamentally focused on finding, with the help of
experiments, whether such maps were actually present in animal and human minds. The first
attempt to use cognitive maps to improve environmental design was carried on by Kevin Lynch
(1960). Lynch, an American urban designer, focused his research on studying how people's
feelings regarding environmental quality could be used to affect urban design; he studied such
feelings through the structure of mental maps of the city that people carry in their mind, and
through interviews.
He analysed through enquiries and surveys the main elements that people use to create such
maps, the process by which they are generated, and the use people make of them in their
everyday life.
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Five elements were found to constitute such maps: paths, edges, landmarks, districts, nodes;
their combination enhances orientation and way finding, what he calls legibility, and identification,
which he calls imageability. In particular, imageability of a place is the sum of properties (shapes,
colours, arrangements) the place has that allow the observer to create in his/her mind strong
environmental images of it (Lynch, 1960: 9). The higher the imageability of a place, the more
people will observe with interest and attention at it; the more people will look at it, the more they
will get familiar with it.
This work, as he then noticed later on in life, just concentrates on the physical structural elements
of the city, leaving out other cues, such as use.
Mental maps: professional perception. Students will illustrate the ‘professional’ perception of the
study area. This task has to be approached as a role-game, with students themselves acting the
role of professional architects and planners. Therefore it is their same perception, in this case,
that they are requested to map out. The following brief history of mental maps gives you an
indication of how to approach this task. You will need to have walked around the study area a few
times and mastered its overall layout. Hide away any OS map and do this simply out of your
memory. It is not a question about correctness, but the most interesting outcomes are about
‘distortions’, that is how you have interpreted a place. We will deal with these in the following
steps:
Each member of the group draws a mental map of Govan (including its boundaries,
reporting in particular the following elements:
Landmarks,
Districts
Edges
Paths
Nodes
Please note that Lynch used a number of questions to support mental maps and to add
information to them. You do not need to use these questions for students’ maps, whilst it
will be very useful to ask them to residents.
Pretend you are moving away from the study area. What will you carry in your
mind?
What do you like about the study area?
What do you dislike about the study area?
A friend of yours is coming to the study area. Could you sketch/list the most
relevant things you would visit and how they are connected?
List distinctive parts of the study area which you feel have special
characteristics worthy of being pointed out to a person who wants to become
more familiar with the city.
Can you draw the route you would walk from X to Y with the most relevant
things you would see?
Collate students’ mental maps. Once all individual maps have been done, students should collate
them in order to highlight similarities and differences. Draw each map on an A1 at an approximate
scale of 1:10,000. This will be useful in then overlaying all layers in order to realize an overall
composite map of each individual ones. Enrich each map with notes, observations, and names.
Students will draw the “composite” map at 1:10,000, summing up findings and notes (fig.1).
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Fig.1. One example of Lynchan analysis worked out by students of the Urban Design Course in Milan in year 2008.
The five elements of cityscape are identified and mapped through a structured interrogation of sources, which
may be either inhabitants (residents in the neighbourhood or district) or ‘professionals’ (students themselves).
Source: Porta and Morello (2008).
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Mental maps: residents’ perception. This will be a fairly challenging task. You will need to do it on site,
stopping people in the streets or visiting groups in their own premises.
Bring with you paper (A3 is as big as you should use, since people will be put off by too large sheets
of paper) and approach people explaining what you are doing and the purpose of this exercise.
Reassure them that it will not take up more than 15 minutes. You might have to draw for them, and
prompt their answers through questions. Refer to Romice and Frey (2003), pp.43-50, for a very
detailed description of this task.
Finally, students should remember that different social groups usually retain different geographies of
their home-place. The level of detail that students could embed in this work is potentially endless, so
they will have to programme on the ground of a careful understanding of available resources.
Follow the same procedure as for the professional analysis detailed above, as well as the specific
instructions on p.47 in Romice and Frey (2003).
Identify/describe Character Areas (CAs). One of the information identified through the mental maps is
Districts, that is areas that share some characteristics such as for example the type of use, the
building typology, the prevalent material used in its development, shop front signage. These can vary.
On top of this, having walked around the area numerous times and talked to residents, you should
have formed an opinion as to which parts of Govan are recognisable and distinctive, unique, similar.
We shall call these Character Areas (CAs). You should map these areas clearly on an OS map at
1:10,000 and identify them with a name (fig.2). Then, describe each of them listing the similarities and
properties that make them distinguishable. This description should be linked to the map and done
through text, images, street sections to name but a few (fig.3).
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Fig 2. Identify and map all character areas. In these case, they have a different colour overlapped to the figure
ground of the area. A side legenda names each one. Separate boards where then prepared to describe in detail
each one.
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Fig 3. In this example, a Character Area is studied through the typical layout of recurrent building types, images of
recurrent and exemplary buildings, materials and street sections. This is just one way to represent it, you can decide
them according to the context.
2. Perceiving and observing the study area (week 2-4):
Permeability. Permeability should be intended as either between districts or within districts. Once
all districts are clearly mapped and described, you will need to report your perception of how easy
it is to move between them (i.e. what defines a district: is it a strong boundary? If so, is it a
motorway, a river, a railway, are there connections across this boundary? How easy can you
cross this barrier to move from one district to the other? This is very important information:
imagine you live in district A but your kids go to school in district B. If the two are very near to
each other but separated for example by a motorway, or a 4 carriage ways, you will not feel
comfortable to let them go to school by themselves. This means that the degree of connection
between the two is fairly low and then, likely in the next phases, you will need to address
simultaneously questions of residential distribution and density, school provision, traffic calming.
Another example to help you understand how important it is to map the perceived connection
between districts is the following: imagine again district A as one with several shops, sitting next
to B, which is instead mostly residential. If the two are well connected, those who live in B will be
well served by facilities and can rely on those in district A for their basic needs. If on the other
hand, there is a motorway or a railway between the two, in the strategic phases you might need to
consider the possibility of adding new services in B.
Describe the accessibility and degree of connection between all district identified.
Perceived connection is very different from objective connection, for example the number of
underpasses across a rail track: if these are dark and unsafe, even if there are 3 in the space of
500mts, people will still be reluctant to use them and the two area cut by the railway will feel
disconnected nevertheless.
Duplicate the 1:10,000 you traced the districts on, and trace easy connection and hard/difficult
connection as they are perceived and pointed out by yourself as well as by inhabitants.
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Fig 4. Railways, highways or heavily trafficked roads in general,, as well as large enclaves of specialist land-uses like
hospitals, airports or military barracks: these all work as “barriers” (light grey in this image of Bologna, Italy) between
neighbourhood and districts that lower their potential (light to dark red) to develop well integrated, thriving
communities across all scales of the urban organism. Source: CAIRE Urbanistica, 2002.
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Fear map. This is a simple but effective exercise that helps you build an overall impression of the
degree of safety and personal comfort of an area. It is fairly straightforward as a concept: a map which
indicates the areas where one feels more or less safe walking/living etc. this map should indicate
gradients of safety or sense of discomfort.
Students will investigate this topic in two ways: again, the first will be about “objective” safety, i.e.
safety as emerge throughout statistical information or direct observation, and the second about
perceived safety, i.e. safety as perceived by inhabitants and city users.
As for objective safety, there are many factors that you can use to explore this concept and represent
it: police reports of incidents (mugging, theft..), signs of vandalism on the street (i.e. broken windows,
litter, murals although murals is not always an indication of vandalism), areas where one can observe
boarded up shops and windows, youth hanging out in groups... After having walked around the area
for a while, you will have picked a lot of these cues. Turn these into a legenda which summarises
elements that can witness or generate fear around the study area and then report them on the map.
Again, the map can be printed at 1:10,000 and illustrated as follows (although you can decide to adopt
a different format).
As for perceived safety, when talking with people in the streets, students will ask them to point out
‘hot’ spots on the map, i.e. to trace a circle on places that they feel as unsafe in their neighbourhood.
They will record a certain number of such maps, qualified by category of responders; the final layout of
this survey will be a map where each of the original individual answers has been reported as a
partially transparent object (use Photoshop, Illustrator or Corel Draw) so that overlapping shadows on
the map will highlight places where perceived fear cumulates (fig.5).
It is important to draw conclusions from this work: for each fear zone, think of the physical context and
try to list the characteristics which you think contribute to make that spot feel unsafe (i.e. secluded; no
escape routes, no activities on the streets in the vicinity...) and add photographs to illustrate your
points. List these for each fear spot, and mark them on the figure ground with a red marker.
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Fig 5. Map showing Instances of robbery in a London area. This is an objective “crime map” which also gives a
clue of the sense of fear that one individual may feel moving around and area. Perceived “fear maps” are
similar but based on answers gathered by local responders instead of statistics or official sources.
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Legibility and imageability. The consistency of some elements in the creation of mental maps is widely
accepted and demonstrated; the interaction and properties of these elements determine legibility and
imageability of places, and then affect evaluation. Urban cognition is connected to Lynch's concept of
imageabilty, and refers to the knowledge of where one is (orientation) and how to get to desired
destinations (way-finding). What we are trying to understand is what affects the choice of some anchor
points (Lynch’s elements) rather than others, or makes them more imageable than others. The
question students will be able to answer with this step is: how do we choose what we look at?
Harrison and Howard (1972) demonstrated that appearance, location and meaning affect the choice of
imageable elements. In a study on the characteristics of the urban features more frequently mentioned
as anchor points among respondents from Ciudad Guayana, Appleyard (Broadbenet, 1980) found that
these are both physical and emotional. In particular, they found three characteristics of both buildings
and spaces, and some of their relative properties, that have major impact on observers' attention and
memory; these were:
Distinctiveness (imageability), influenced by intensity (what Appleyard calls measure of
presence) and singularity of the contour, size, shape, surface, quality of elements.
Visibility, influenced by location, focus of action and measured by 1) the number of
people who might regularly see the anchor point, 2) its presence at important decision
points or points of transaction on the city's circulation system and 3) the distance and
centrality in the line of view).
Role and inferences were considered as constituting the community significance, a
dimension measurable by its use intensity, use singularity and by its symbolic, political,
economic, aesthetic or historic significance (ibid.:140).
Other studies have confirmed the factors identified by Harrison and Appleyard, together with building
significance, accessibility from street, uniqueness of style, naturalness (mainly for buildings). In
conclusion there are some space-buildings aspects that have a main role in imageability, such as
exposure, significance and visual contrast). Imageability affects notation and memory, but does not
necessarily determine appreciation, that is positive feelings towards what is observed. Still, imageable
features are those towards which it should be possible to guide evaluation, because they are easily
identifiable, and more commonly used as references.
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For this exercise, students will be requested to map all elements in the study area that they feel as
distinctive, visible and possess a special role on a map 1:10,000 (fig.6); some of these should have
resulted from discussion with the residents you met for the mental maps exercise. Then, they need to
trace overall and district imageability through the study area: the scope of this task is to understand
how its structure (with elements) performs to generate a tissue that can be understood and navigated
comfortably by people. Where this is not successful, where for example you get lost easily, or there
are no points of reference, we will need to concentrate intervention in the next phases.
Fig 6. Kevin Lynch’s analysis of the “visual elements” of Scolley Square, Boston.
Imageability is defined as: “That quality in a physical object which gives it a high
probability of evoking a strong image in any given observer”, Lynch (1997,
c.1960), p.9. Source: Lynch (1997, c.1960), p.179.
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Maintenance. The state of maintenance and personalisation of an area can be very revealing for
designers. Research has in fact demonstrated that high levels of personalisation can be both signal of
poor acceptance of the place or the opposite; that the management and regulations of spaces,
including the service of maintenance, safety and surveillance, as well as the possibility to use spaces
for social activities which derives from their state of maintenance, are factors that can satisfy the need
for creativity, self-expression that people have and can exercise in the area they live.
Also, factors such as maintenance of the house and neighbourhood, relationships with the
neighbours, participation and neighbourhood activities are amongst the factors most regarded by
people about their residential settings [in a study conducted in Santiago de Compostela, Garcia- Mira
and Sabucedo (1997) demonstrated that the three principal factors affecting the perception of
neighbourhood quality were social status, the quality of planning and maintenance and spaciousness.
However, to each of these principal factors other properties tended to be associated in respondents’
answers. In particular, to status was associated the concept of centrality and the presence of symbolic
elements; to planning and maintenance that of safety, security and uncertainty, to spaciousness that
of communication with the city and legibility.
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Recording the variations in the degree of maintenance and personalisation of a neighbourhood and its
districts (fig.7) is fundamental to understand a) to what extent people are comfortable and feel safe in
using spaces, b) their exercise of territoriality through personalisation or their desire to better the area
through improvement of personal space, as a positive contribution to the overall. There are several
other conclusions that can be derived, and it is up to your group to summarise the findings of this
investigation and represent them in a meaningful way.
Fig 7. Behavioral Traces Map of a park area in San Francisco.
Source: Cooper-Marcus and Francis, 1998, p.351.
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Street Front Assessment. Street front assessment is an exercise aimed at understanding several
simple spatial characteristics of street fronts that heavily impact on communities and the life of
inhabitants in many different ways. These characteristics range from the number of visible buildings to
the continuity of the street front, from visual richness to maintenance, and many others. Students will
be requested to make their inevitably subjective evaluations a bit more objective by making it clear
what are the criteria that drive their work in a sort of small handbook (fig.8). Students will be led to:
Map the quality of street frontages.
Understand possible correlations between the quality of street fronts and recursive
collective behaviours.
3. Experiencing Place Report (week 5):
Produce the report. The Experiencing place report is a document that summarizes knowledge
achieved throughout both metal mapping and observation. Therefore, the Report is certainly a
synthesis of the whole WP1; the Report is a miscellaneous of different communication
techniques, ranging from textual to graphic and numeric/statistical or others (including
photographs).
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Fig 8. This is an example of a handbook created to “objectivise” the subjective attribution of values to
street fronts: criteria are clearly expressed and illustrated by visual and textual techniques.
Source: Porta and Morello, 2006.
Fig 9. Plan showing street frontages dominated by ground facades in the three best categories. Source:
Gehl, 1994, p.18.
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WP2. COMPARING PLACE
0. Construction of the urban model (week 1):
This step is the prerequisite to fulfil the WP2. The base for the entire set of analysis consists in the
reconstruction of 3 urban areas proposed by the students plus the study area.
Which sites to choose?
First, students have to carefully read the map of Glasgow, trying to understand its different components
and evolutionary stages. This phase of reading is suggested, in order to better choose the areas of
analysis. For instance, the sites should represent three different typologies of urban textures inside the city
of Glasgow. They have to address three different historical construction periods as follows:
1) Site 1: the historical area, typically the city centre with traces of the ancient urban texture;
2) Site 2: the pre-modern city, i.e. an urban texture designed in the XIX or beginning of the XX
century before the age of car dependence.
3) Site 3: the modern city corresponding to a human settlement built after the II WW.
4) Site 4: A significant extraction from the study area that sufficiently represents the character of the
urban texture (streets and blocks layout).
It is important that the centre of the selected sites corresponds to a significant urban node, such as a
transportation hub or a central place. This point has to be a central location, a point of reference for the
neighbourhood.
The selection of those urban areas has to be discussed together with the staff and need to be approved
before starting the analysis. This step should happen in the very first days.
All the areas should be characterized by the same extension, i.e. a square that measures 800m by 800m.
The indicated measures are not casual, because they precisely represent the reachable walking distance
within the time of 5 minutes, if measured from the geometrical centre of the square.
Which information needs
to be represented in maps/models?
After the 4 sites have been selected, different models have to be produced for each site:
Vehicular street network. The street network, built as a simple scheme is composed by links
(linear street segments with no depth) and nodes (indicate it with circles at the intersections of
links). The intersections can be distinguished depending on the number of links converging on it;
please, take into account the following 5 categories: more than 4-way, 3-way and cul-de-sac) and
assign to each type a different colour (i.e. the colour of the circle that denotes the knot). Notice
that you cannot have 2-way intersections.
Whole ped/veh paths network. Do the same as for vehicular network but completing the graph
adding all links and nodes of the pedestrian and cyclist paths. This work must be coordinated
with Group 5.
Block structure. This is about the black and white representation of the block structure. Blocks are
filled in black and the empty spaces (streets and other public spaces, non-urban land) are left in
white (fig.1).
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Fig. 1. A black and white representation of the block structure. This image also represents
the porosity of the urban fabric, and information that not always is essential in
block analysis. Blocks can be in that case filled entirely in black without detailing
internal voids.
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1. Connectivity (week 2-3):
A set of structural indicators of connectivity and accessibility is presented here. The parameters are
organized in two main sections. The first section includes indicators related to the street network; the
second one considers indicators derived from the analysis of the urban block. All the measures have to be
computed on each case-study area (4 selected sites as explained above). At the end of the section 3 of
this chapter, a table that summarize the suggested indicators is provided. Please, refer to that scheme to
organize your work.
In order to analyse the connectivity of urban areas we can investigate different strategies. We propose to
classify connectivity measurements depending on the object of observation. In fact, to measure the
connectivity we can simply analyse the street network but also its negative correspondent, i.e. the urban
block interpreted as the space delimited by streets. In this sense, connectivity indicators are de facto
morphological indicators. Cities can deploy urban design standards that regulate the size and the length of
streets and/or they can suggest rules that control the size and the shape of urban blocks. A list of
connectivity measurements follows.
Street network indicators. Numerous indicators can describe a network and these are mainly
borrowed from graph theory. A network is defined as the interconnected system of elements: the
elements can be interpreted as the nodes and the connection as the link of the network. From the
investigation of these basic elements, nodes and links, we can derive several indicators that can
take into consideration geometrical or topological spaces.
Intersection Density. A first measure is to count the number of nodes per unit area. The
higher is the number of intersections the greater is the connectivity. The area of investigation
can encompass for example an urban structural unit (an area with similar morphological
characteristics). This measure is also used by LEED ND (2008).
Street Density. The number of linear extensions of streets per unit area is computed. This
indicator can be obtained by counting the linear kilometres of street (linear extension of street
segments to be summed together) per unit area of analysis (for example 1 square kilometre).
Internal connectivity or Connected Node Ratio (CNR) can be measured as the number of
street intersections divided by sum of the number of intersections and the number of cul-desacs. The higher is the ratio, the greater the internal connectivity. As suggested by the
INDEX model (Criterion Planners Engineers, 2001), values should not be less than 0.5, and
0.7 and higher are recommended.
Link-Node Ratio. The ratio of the number of links to the number of nodes. A perfect grid has
a ratio of 2.5. Reaching 1.4 is a good target in new human settlements. The Link-Node Ratio
is useful, when a comparative study between two conditions at different times on the same
area is undertaken. Anyway, this index is unrelated to the sizing or spacing of the grid. This
means that the same grid at different scales has the same value, suggesting that some
additional considerations about the length of street intersections have to be taken into
account.
Connectivity of the object, typically the neighbourhood. This can be measured counting the
number of existing intersections and street segments and computing their lengths, thus
revealing the presence of cul-de-sac like urban layout or, on the contrary, a rich
interconnected urban texture. Internal and external connectivity of a neighbourhood are
introduced. Internal connectivity can be measured as the number of street intersections
divided by sum of the number of intersections and the number of cul-de-sacs (the higher the
ratio, the greater the internal connectivity); external connectivity is the median distance
between ingress/egress points in meters (the shorter the distance, the greater the external
connectivity).
Grid pattern ratio. It defines the rate of the investigated area which is included in a grid
pattern. We distinguish between a strong and a weak grid pattern ratio.
The strong grid pattern ratio defines the rate of the investigated area which is included in a
perfect grid pattern. A grid pattern is characterised by 4-way intersections and an urban block
is included in the grid pattern if the nodes at all its corners are 4-way intersections (fig.2, left).
The weak grid pattern ratio defines the rate of the investigated area which is included in a
almost perfect grid pattern. A grid pattern is characterised by 4-way intersections and an
urban block is included in the grid pattern if all the nodes except one at its corners are at
least 4-way intersections (fig.2, right). This measure represents a less restrictive condition
than the previous indicator.
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Analysis brief 04: Experiencing and comparing place, 2012/13.
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Fig. 2. Strong grid pattern ratio (left) measures how much of the study area is included in
blocks that have all their corners constituted by 4 ways intersections. Weak grid
pattern ratio (right) is the same, but also blocks with all but one corners on 4 ways
crossings are included. The patched areas are included in the grid.
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Street network permeability. The permeability index tells how integrated the street network is.
On every intersection of the street network we have to indicate the numerical value of the
allowed possibilities of moving forward. This can be done by summing all the possibilities on
each arch converging on the intersection (fig.3). Please notice, that if there is the chance to
turn around and go back, this movement should also be summed to the value. Two different
computations need to be conducted: one on the pedestrian network and the second on the
vehicular one. Notice that pedestrians have a number of choices always equal to the number
of converging links, while for vehicles this range of choices depends on admitted turns.
Finally, the difference of the permeability of the pedestrian and the vehicular network can be
computed. This latter value represents also an accessibility index.
Fig. 3. Movements allowed on a 4-way intersection; on the left, the count on the vehicular network
(2+2+3+0=7 movements) and on the right, the count on the pedestrian network (4+4+4+4=16
movements).
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Urban block indicators.
Block Area. Defining the area of the block implies the definition of the street network that
supports the urban texture. The smaller are the blocks the greater the connectivity. This
indicator is very simple and immediate.
Block Density. Similarly to the previous index, determining the number of blocks per unit area
(typically 1/ha) informs about the granulometry of the urban texture. This index permits more
flexibility than the block area index in the design of neighbourhoods, since it allows to provide
more diversity in the process of sizing blocks.
Block Length. Together with the block area, controlling the maximum extension of the
frontage of the block is a way to avoid elongated or fragmented shapes that could rather
reach the opposite effect and decrease the connectivity of the urban texture.
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2. Accessibility (week 2-3):
Accessibility indicators. A direct consequence of increasing connectivity of a street network is to
provide greater access and communication. Citizens living in cul-de-sacs-like areas have simply
less accessibility to places, because the connectivity of their houses is low and they have to travel
more to access points of interests (transportation nodes, commercial uses, services, etc.).
Therefore, it is really difficult to clearly separate measures of accessibility from measures of
connectivity. In general, we can measure accessibility by determining those existing relationships
between the point of observation and the point of interest. A list of indicators follows:
Distance of the object to a particular target (centre of the district, transportation hub,
commercial uses, public park). This index can be computed after determining the centroid of
the object itself and then measuring the Euclidean distance to the target. Pedestrian access
is usually encouraged if targets are within a ¼ - mile (or 400mts) distance (Duany and PlaterZyberk, 1992). In order to calculate this indicator we refer to the PedShed Analysis (fig.4).
Rate of connectivity. Counting how many points of interest are included in a defined area, like
for example inside the ¼ - mile radius walking area. Subcategories like for example retail,
green areas, transportation can be the object of the analysis (refer to the figure below). This
analysis produces maps that can describe the distribution of accessibility values if computed
on a fine-grained grid.
For example we propose the following procedure:
To count the number of existing activities per subcategory (we consider: residential,
shops, offices, health, entertainment, utilities);
To calculate the variety index (or diversity index) of the categories that are present
around the point of observation.
Simpson Diversity Index = 1- Σ (n/N)2
where
n = the total number of units in a single category
N = the total number of units in all categories.
3. Pedshed analysis (week 2-3):
Pedshed analysis. PedShed analysis aims at identifying the permeability of the street network for
pedestrian (fig.4). Students are invited to take the map with the pedestrian street network and
trace a circle with radius of 400 meters. The analysis has to be performed inside the circle only.
Starting from the centre of the circle we have to take all possible paths people can take for a
linear distance of 400 meters. In order to do this, please measure a solid poly-line drawn in the
centre of the street and stop when the poly-line reaches 400 meters. Once all possible ways have
been drawn, build the perimeter that includes all the reachable places. These latter have to be
filled with a uniform colour (for example in red, like in Figure 4 left, presented below). Please,
refer to the lots inside the block as the minimum units to be considered to trace the reachable
area: this allows highlighting also small portions of blocks in case of large blocks, that otherwise
would have been totally included or discarded.
After this step, the percentage of the reachable area can be computed by simply calculating the
ratio of the reachable area (take the entire area of the polygon, streets included) divided by the
area of the circle.
4. Comparing Place Report (week 4-5):
Produce the report. The Comparing place report is the second part of the final document of this
research. The Report is a miscellaneous of different communication techniques, ranging from
textual to graphic and numeric/statistical or others (including photographs).
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Analysis brief 04: Experiencing and comparing place, 2012/13.
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Fig. 4. An example of a PedShed analysis. Source: ISTP Murdoch University and Western Australia Ministry for
Planning, 2001.
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Analysis brief 04: Experiencing and comparing place, 2012/13.
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The table below (tab.1) summarizes previous indicators and should be used as a reference by students.
site 1
name
Connectivity Indicators
site 2
name
site 3
name
site 4
name
unit
Connectivity Indicators related to the street network
Intersection Density
Street Density
Internal Connectivity or Connected Node Ratio (CNR)
Link-Node Ratio
Connectivity of the object
Grid pattern ratio
The strong grid pattern ratio
The weak grid pattern ratio
Street network permeability
Connectivity Indicators related to the urban block
Block Area
Block Density
Block Length
Accessibility Indicators
unit
Distance of the object to a particular target
Rate of connectivity
PedShed Analysis
unit
Percentage of area reachable within 400 meters radius
Percentage of area reachable within 800 meters radius
Table 1. The list of indicators presented in WP1.
An example of application of connectivity and accessibility indicators inside an urban
design code: the LEED ND pilot version
NB: The following section is not part of the exercise, but it only describes an example of an
application of urban connectivity and accessibility indicators inside an urban design certification
procedure, namely LEED ND in its pilot version. This procedure can be taken into account by
students once the general master plan has been developed. For instance, the following subsections
refer to those parts of the procedure that explicitly apply connectivity indicators.
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LEED ND| Smart Location & Linkage, SLL Prerequisite 1: Smart Location
OPTION 2 – ADJACENT SITE WITH CONNECTIVITY (fig.5).
Locate the project on an adjacent site with pre-project connectivity of at least 150
intersections/sq. mile within a half circle using a radius cantered on the midpoint of the
adjacent portion of the project perimeter. The radius of the half circle must be ¼ mile, or the
length of the adjacent portion of the perimeter, whichever is longer; and if the project contains
streets, its connectivity cannot be less than the connectivity of the surrounding area measured
within the half circle; and design and build the project with at least one through-street and/or
non-motorized right-of-way (non-motorized rights-of-way may count for no more than 10% of
the total) intersecting the project boundary at least every 800 feet.
Fig. 5: LEED ND, Smart Location, adjacent site
with connectivity
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LEED ND | Smart Location & Linkage, SLL Credit 1: Preferred Locations
OPTION 2 – CONNECTIVITY (fig.6).
Locate the project in an area that has the following connectivity within a 1 mile radius from the
perimeter of the site boundary:
a. 400 or more intersections/square mile or greater (5 points)
b. 300-400 intersections/square mile (3 points)
c. 200-300 intersections/square mile (1 points)
Fig. 6. LEED ND. Preferred Locations, connectivity
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Analysis brief 04: Experiencing and comparing place, 2012/13.
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LEED ND | Neighbourhood Pattern & Design, NPD Prerequisite 3: Connected and
Open Community Required
OPTION 1 – PROJECTS WITH INTERNAL STREETS (fig.7)
Design the project such that its internal connectivity is at least 150 intersections/square mile.
Designate all streets and sidewalks that are counted toward the connectivity requirement as
available for general public use and not gated. Gated areas are not considered available for
public use, with the exception of education and health care campuses, and military bases,
where gates are used for security purposes.
Fig. 7. LEED ND. Connected and Open
Community. Projects with internal
streets
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LEED ND | Neighbourhood Pattern & Design, NPD Credit 6: Street Network (fig.8).
Locate and/or design the project such that its internal connectivity, and/or the connectivity
within a 1/4 mile radius from the geographic centre of the project, falls within one of the
ranges listed in the following table:
Connectivity
(intersections/sq. mile)
> 300 and ≤400
> 400
Points Earned
1
2
Fig. 8. LEED ND. Connectivity schemes of street networks.
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Analysis brief 04: Experiencing and comparing place, 2012/13.
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4.3 Deliverables
The Experiencing and comparing place report is intended as the final deliverable of this analysis package,
which will include:
WP1:
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Composite mental maps of students
Composite mental maps of residents
Comparison of composite mental maps and discussion
Map of Character Areas and individual description (1or more boards for each)
1 map to describe barriers and connections between districts
1 fear map
1 legibility/imageability map with comments
1 maintenance map overall, plus detailed district ones where necessary.
WP2:
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Maps and tables of Connectivity.
Maps and tables of Accessibility.
Maps and tables of Ped Shed.
CONCLUSIONS:
‘Lessons learnt’ layout, which will include maps, texts and figures of main lessons to be taken into
consideration in successive proposals and projects in the study area.
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4.4 References
WP1. Experiencing Place
Broadbent, G. Bunt, R. Lorens, T. 1980, Meaning and Behavior in the Built Environment, John Wiley &
Sons, Chester.
CAIRE Urbanistica, 2002, Studies for the General Plan of the city of Bologna, Italy.
Cooper-Marcus, C. Francis, C. 1998, People places: designing guidelines for urban open space, Van
Nostrand Rehinold, New York.
Garcia-Mira, R. Arce, C. Sabucedo, J. 1997, Perceived quality of neighborhoods in a city in Northwest
Spain: an individual differences scaling approach, Journal of Environmental Psychology, 17 243-252.
Gehl, J. 1994, Public space and public life in Perth, Report for the Government of Western Australia adn
the City of Perth.
Harrison, DJ. Appleyard, WA. 1980, The role of meaning in the urban image, in Broadbent et al, 1980,
Meaning and Behavior in the Built Environment, John Wiley & Sons, Chester, p.163-183.
Lynch, K. 1960, The Image of the City, MIT Press, Cambridge, MA.
Nasar, J. 1998, The Evaluative Image of the City, Sage Publications, London, UK.
Porta, S. Morello, E. 2006, Students’ work at Urban Design Course, Politecnico di Milano, Facolta’ di
Architettura Civile.
Romice, O. Frey, H. 2003, The Communities in Action Handbook, University of Strathclyde, Glasgow, UK.
WP2. Comparing Place
Criterion Planners Engineers, 2001, INDEX PlanBuilder User Guide, Portland, OR
(http://www.crit.com/documents/planuserguide.pdf).
Duany A.M., Plater-Zyberk E., 1992, “The Second Coming of the American Small Town,” The Wilson
Quarterly, 4, 19-50.
ISTP Murdoch University and Western Australia Ministry for Planning, 2001, Sustainable Urban Design.
Practical fieldwork project, Text booklet at the Sustainable Design Course, Murdoch University,
Perth, WA.
Kanski, K.J., 1963, Structure of Transportation Networks: Relationships Between Network Geometry and
Regional Characteristics, University of Chicago Press, Chicago.
USGB, 2008, LEED for Neighborhood Development Rating System.
(http://www.usgbc.org/ShowFile.aspx?DocumentID=6146)
Rodrigue, J. P. Comtois, C. Slack B. 2009, The geography of Trasport System, Routledge, New
York.
(http://people.hofstra.edu/geotrans/eng/ch2en/meth2en/ch2m1en.html).
References for working instructions:
Porta, S. Morello, E. (2006), Students’ work at Urban Design Course, Politecnico di Milano, Facolta’ di
Architettura Civile.
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