Measuring, identifying and analysing
street crime risk
Dr Jake Desyllas
Spencer Chainey
Intelligent Space Partnership
The Jill Dando Institute of Crime Science
www.intelligentspace.com
www.jdi.ucl.ac.uk
Introduction
• Initiatives for tackling street crime,
–
–
–
–
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Targeted to hotspots
Gone down
Lowered the heat
Sustainable?
No consideration of risk of street crime to the pedestrian
• Street crime statistics
– Number of crimes
– Rate per 1000 population per annum
National average robbery rate = 2.1 per 1000 population per annum
City of London = 6.3
Bournemouth = 1.7
08/03/2004
Street crime rate
• What use is this rate?
– Designing policing responses and crime reduction initiatives?
– Public reassurance?
– Town centres or ‘busy’ areas?
• requiring the areas it affects to always have to explain and give caution to these
statistics)
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Street crime risk
• Questions we want to ask?
– MEASURE: What’s the probability of walking down a particular street
in Central London and being a victim of robbery or theft snatch?
– IDENTIFY: Are the patterns of street crime risk when calculated
using the on street population different to volume hotspots?
– IDENTIFY: Are the patterns of street crime risk when calculated
using the on street population different to rate maps that use resident
population as their denominator?
– ANALYSE: Are there certain differences that make areas high crime
volume/high crime risk, high crime volume/low crime risk, low crime
volume/high crime risk.
Hypothesis:
The use of pedestrian counts generated from pedestrian modelling, when calculated
against street crime data will provide a more accurate picture of the probability of being
robbed or a victim of theft snatch.
Street crime: Robbery to the person and theft snatch from the person
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Study area - Westminster
•
London Borough of
Westminster
•
Study area
– CCZ of LB
Westminster
•
Street crime (2003)
– 1138 crimes
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Robbery in study area
Number of daylight robberies: 125
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Number of night time robberies: 362
Snatch theft in study area
Number of daylight snatch theft: 277
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Number of night time snatch theft : 374
Resident population in study area
Resident population in study area (2001 Census): 40,756
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Robbery in study area (rate and volume)
Daylight robbery: 3.1 per 1000 population per annum
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Snatch theft in study area (rate and volume)
Daylight snatch theft: 6.8 per 1000 population per annum
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Graph of differences day/ night pedestrian flows
9000
Pedestrian Flow (Saturday)
Day Time Pedestrian Flow
8000
7000
Average PPH
6000
5000
4000
3000
2000
1000
0
00:00
02:00
04:00
06:00
08:00
10:00
12:00
Time
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14:00
16:00
18:00
20:00
22:00
Graph of differences weekday/weekend pedestrian flows
600
Weekday
Weekend
Average Pedestrian Flow
500
400
300
200
100
0
08:00
09:00
10:00
11:00
12:00
13:00
14:00
Time
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15:00
16:00
17:00
18:00
19:00
London Pedestrian Model: Approach
Measurement
of Key
Variables
Sampling of
Observed
Pedestrian
Flows
Model independently
Validated by TfL
MRA model
Model applied to
larger Central
London Area
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Testing against
further samples by
TfL
Pedestrian Model: key factors
Visibility
Transport accessibility
Land use
Capacity
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Daytime pedestrian population per street segment (model)
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Map of All Crime
Snatch Theft
Robbery
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Map of All Crime
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Snatch theft risk (pedestrian population)
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Robbery risk (pedestrian population)
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Measure – what’s the probability of being robbed?
• Pedestrians that walk along this street
segment on average per hour during daylight
hours: 5,047
•What’s the probability of walking out of Oxford
Circus tube station, turning left towards
Tottenham Court Road and being robbed or
having my bag snatched?
– Robbery = Zero
– 0.0004 per 1000 pedestrians per annum
That is, it will take 2,500,000 people to
walk this stretch of street before someone
has their bag snatched
- OA 134 per 1000 population per annum
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Next stages of research
•
IDENTIFY:
– Where’s the riskiest place in Westminster?
• Streets
• Postcodes
• Worst areas (preliminary results) – 1 in 600,000 robbed and
1 in 250,000 theft snatch
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ANALYSE:
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–
–
–
•
High crime/high risk areas
High crime/low risk areas
Low crime/high risk areas
Threshold values – how many people does it take to walk down a street for
the them to act as guardians?
Not looking to replace hotspots – add a different dimension.
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Summary
• Better statistics of the levels of magnitude of being a victim
of street crime
– Public reassurance
• Geographic patterns are different
• Extension of the work (if we get funding)
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–
–
–
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Add the Underground Stations to the maps?
Extend the pedestrian model to other areas
Risk patterns by time of day – night time pedestrian movement, hour counts.
Explore risk generators: what makes an area hot?
Importance of natural surveillance?
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Thank you
08/03/2004