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DOMESTIC
BURGLARY
....................... .....................
..................... ........................ analysis
of crime location and spatial accessibility, UK
CRIME
THE
SPACE SYNTAX ONLINE DATABASE OF CRIME AND SPACE STUDIES
To facilitate an informed debate on
the issue of crime and spatial design, Space Syntax has
decided to create an online database of studies so that
people can access and assess the first hand evidence for
themselves. The first study on the site is "DO
BURGLARS UNDERSTAND DEFENSIBLE SPACE?" by Bill
Hillier and Simon Shu. This paper was originally published
in the April 1999 edition of Planning In London and is
reproduced with permission (contact 020 7834 9471 for
information on Planning in London).
Additional studies will be added to
the site as soon as they are available. The forthcoming
article "CRIME AND URBAN LAYOUT: THE NEED FOR EVIDENCE"
by Shu and Hillier, due to be published in the forthcoming
book from the Institute for Public Policy Research (IPPR):
'Key Issues in Crime Prevention, Crime Reduction and Community
Safety' (eds. Ballantyne S, MacLaren V, Pease K), will
be soon available in PDF format.
CRIME AND SPACE RESEARCH: THE NEED
FOR RIGOUR
AN INTRODUCTION TO THE DATABASE
BY PROFESSOR BILL HILLIER
Crime and space research has poor
record for a number of reasons. First, too little effort
has been made to isolate the effects of spatial design
from those of social composition. In residential crime
this is critical. Markets forces and local bureaucracies
alike tend to ensure that better of people end up in good
areas and less well off people in less good areas. Since
more crime occurs in less good areas, it is hard to distinguish
the effects of space from those of the social process
that put people there. Second, too little attention has
been given to spatial detail since studies have been at
the level of the estate or the area rather than the individual
crime. Third, too many different kinds of crime have been
lumped together. It is likely that each type of crime
has its own spatial logic which need to be identified.
Fourth, studies have been too loose statistically in dealing
with the interaction between factors, and so the work
has been criticised.
The first paper on the database deals
with the issue of domestic burglary (and to a lesser extent
car crime) and how it is facilitated or inhibited by the
design of public space. Are cul-de-sacs really safer than
through roads? Does it help to separate vehicles from
pedestrians? Do you really benefit from having small groups
of neighbours, or are you safer with more ? Should we
group houses into 'territorial' units? Or is it better
to be on a more anonymous street?
There are four problems to be solved
to show an influence from spatial layout on crime and
begin to answer these questions. First, you have to take
out the background effects of social composition and location.
Burglary rates for inner urban areas are10.3%, 6.3 for
'suburban' areas and 3.9 for rural. Owner-occupiers (5.3%)
with good incomes (5.6%) are much less likely to be burgled
than renters (8.9%) on low incomes (8%). Because cul-de-sacs
are concentrated in newer, outer urban areas, and tend
to be occupied by owner-occupiers on better incomes, while
inner urban areas have older through streets, with more
renters and lower incomes, social effects can easily be
mistaken for spatial effects.
Second, you have to show how each
crime is facilitated by spatial design. For example, for
burglary, how the burglar accessed the dwelling from public
space is critical, not the address. There is no advantage
in having an address in a 'safe' cul de sac if the burglar
gets in from a footpath behind your back garden. Third,
you have to distinguish between different types of crime,
and make research crime specific because different crimes
relate to space in different ways. Picking pockets thrives
in crowded shopping areas, public order offences will
concentrate on main streets, since this is where the main
pubs and takeaways will be, and so on. Fourth, to establish
that some types of location are safer than others you
have to establish the rate of crime against the number
of targets, not simply show the numbers of crimes.
All of these issues are dealt with
in our work. We selected towns with very different social
mixes, and sub-areas with both different spatial layouts
and different social composition and looked for common
patterns in spite of these differences. We focused specifically
on domestic burglary in residential areas (and to a lesser
extent car crime and vandalism) in order to deal with
the type of crime that most affects ordinary people with
the exactness that is needed. We mapped the exact part
of public space from which the burglar gained access to
the crime site, and we established the degree to which
different layout factors affect rates of crime in different
locations.
Our results are pretty much common
sense. They show that the spaces from which you were least
likely to be burgled were well integrated linear residential
through roads with good numbers of 'intervisible' dwellings
facing the road on either side with no gaps. Where through
roads did not have these properties they quickly became
much more vulnerable. Cul de sacs which did have these
properties, that is, were simple, linear and continuously
faced with dwellings on both sides, were safer than tortuous
complexes of cul de sacs with small segregated groups
of dwellings in visually separated spaces. In 'complex
cul de sacs', the first line in from the through road
- and therefore visible from it - was much safer than
the lines after the first corner was turned inside the
complex.
Most important of all, our results
showed that factors to do with position in the overall
layout and those to do with the immediate vulnerability
of the dwelling - having a hidden driveway, or an exposed
side or back fence - interact, so you could not say that
this type of space was safer than that type without taking
into account the other factors. All had to be present
together to maximise safety. But when all the safety features
were in place, then spaces which allowed through movement
were safer than those which did not.
HOUSING
New Space Syntax findings on the link between crime and
design challenge the widely accepted benefits of 'defensible
space'. Space Syntax studies show that streets are made
safer by the presence of passers-by, as well as residents.
Using Space Syntax, through-movement and 'natural surveillance'
potentials can be established early on in new housing
projects. Detailed studies of social
decline and crime patterns in existing housing layouts
are being used to identify problematic areas and understand
the factors which increase vulnerability.
LESSONS FROM THE ANALYSIS OF 20TH CENTURY HOUSING ESTATES
Space Syntax studies provide empirical descriptions
of current spatial and social structures in housing estates
which can be used to measure the likely pedestrian effects
of redevelopment proposals and, where relevant, make suggestions
for improvements to these which will directly benefit
pedestrians of all ages.
Space Syntax analysis of urban areas built before the
twentieth century has - despite the heterogeneity of individual
case studies - found a number of general shared characteristics.
First, the tendency towards larger gridblocks with outward
facing dwellings and a clear distinction between public
and private space. Second, the creation of simple pedestrian
route networks involving relatively few changes of direction
between most origins and most destinations. Third, a direct
correlation between the accessibility of individual streets
(defined mathematically, see Hillier and Hanson, 1984)
and the individual levels of pedestrian activity on these
streets. Fourth, the inclusion of 'strangers' or non-residents
among the residential pedestrian community. Fifth, the
sharing of streets by people of all age groups and both
sexes.
The design of residential estate layouts in the Twentieth
Century has - in many, if not most, cases - turned these
rules on their heads. Grid blocks have been downsized,
dwelling entrances have been arranged often to suit aspect
and solar orientation than any other relationship, and
as a result the boundaries between public and private
space have been blurred; pedestrian route networks have
been complicated - and in some cases become labyrinthine;
the link between accessibility and movement rate has weakened;
strangers have tended to walk around estates rather than
through them since this normally involves fewer changes
of direction; and finally, the link between children and
adults has weakened since, with the proliferation of spaces
brought about by the downscaling and complicating of the
urban environment, children have tended to explore isolated
areas and the 'natural' link to adult supervision has
been lost.
These effects are described by Hillier who details a correlation
between the radical spatial design of Twentieth Century
housing estates and their largely negative social outcomes
(1). The absence of strangers - whose presence is taken
for granted by residents of 'traditional' housing areas
- and the separation of adults from children - leading
to the perception of fear among vulnerable older people
who encounter groups of young people as they move through
segregated areas of modern housing estates - creates a
combined effect which went directly against the regenerative
intentions of designers, developers and authorities. In
this way, many housing estates which were originally recognised
for their design qualities - such as the Maiden Lane Estate
in Camden and the Marquess Road Estate in Islington -
soon became some of the least desirable places to live
(2).
By employing space syntax analysis it has been possible
to study individual estates and measure the degree to
which the spatial and social characteristics described
previously are present. These studies have usually comprised
three parts: the computer modelling of spatial networks;
the direct observation of pedestrian activity; and the
statistical correlation of the twin databases to examine
the relationship between spatial design and social outcome.
For example, recent computer modelling studies of the
Chalkhill, Maiden Lane and Elm Village Estates in north
London show the degree to which each of these housing
layouts is segregated from its urban context (Figure 1a/1b,
where the colour of each street represents the degree
of accessibility and potential pedestrian movement on
that street from red = most accessible through orange,
yellow and green, to blue = least accessible).
Figures 1c and 1d present the findings of a direct observation
study of the Chalkhill Estate where distinctions have
been drawn between the use of space by men, women and
children. Figure 1c shows how the density of pedestrian
activity falls sharply from the streets surrounding the
Estate towards the south and east. By contrast, children
cluster in spaces towards the heart of the Estate, creating
a separation between old and young people. Analysis against
the findings of the spatial computer model produces two
key results:
* first, that the pattern of adult pedestrian movement
is directly related to the degree of spatial accessibility
with more accessible streets carrying more pedestrian
movement;
* second, that it is the downscaling of urban space which
creates the conditions for children to explore the less
accessible parts of the estate which adults normally avoid.
Other space syntax studies have shown that the complex
configuration of urban space in housing layouts such as
the Chalkhill Estate - when combined with the effects
of inward-facing dwellings - can create a distinct pattern
of fear among pedestrian users, as well as an actual pattern
of crime and anti-social behaviour. For example, current
space syntax studies in housing estates across the South
of England report a direct correlation between the location
of criminal behaviour (in this case burglaries) and spatial
segregation. Results also indicate that an effective pattern
of movement is itself one of the most efficient ways to
control crime in housing estates (3).
These findings have led researchers to question the concepts
of 'enclosure' and 'defensible space' which have for some
time guided the design of housing layouts. The Space Syntax
findings support the criticism of other urbanist, such
as Jane Jacobs who argued that the city has to abandon
design principles which destroy the sense of harmony,
safety and control in residential areas.
1 Hillier, Bill "Can Architecture Cause Social Malaise",
Chapter 5 of "Space is the Machine"
Cambridge University Press, 1996
2 Hunt Thompson Associates. "Maiden Lane: Feasibility
Study" for the London Borough of Camden, 1988
3 Jacobs, Jane. The Death and Life of Great American Cities.
Penguin Books, Hammondsworth,1961.
CONFERENCE
PAPERS
1997 'Housing Design
and the Virtual Community' (with M Major, A Penn and
Professor B Hillier) Making Cities Livable Conference,
Charleston, USA.
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