4. Neil Gershenfeld
Director of MIT’s Center for Bits and Atoms
“Computer science is one of the worst things to
happen to computers or to science because, unlike
physics, it has arbitrarily segregated the notion that
computing happens in an alien world.”
21. Why Walkability?
Adds 5-10 % to house prices
@ the heart of the cure to the health-care crisis in US
Carbon saving (light-bulbs 1 year= living in a walkable for 1 week)
neighborhood in 1 week)
24. “The General Theory of Walkability explains how, to
be favored, a walk has to satisfy four main
conditions: it must be useful, safe, comfortable, and
interesting. Each of these qualities is essential and
none alone is sufficient.”
25.
26. Walkonomics is a composite score of
1. Road safety (#accidents)
2. Easy to cross (street type + traffic)
3. Sidewalks (width)
4. Hilliness
5. Navigation (signs on street)
6. Safety from crime
7. Smart and Beautiful (e.g., #trees, close parks)
8. Fun and relaxing (shops, bars, restaurants)
27.
28.
29. Hypothesis
A street’s vitality is captured in the digital layer
(there might be digital footprints that distinguish walkable
streets from unwalkable ones)
31. Reliability
Measurement error
borrow measurement procedures from the literature
(e.g., a buffer of 22.5 meters around each street’s polyline)
Specification error (Flickr/Foursquare biases)
normalization measures (e.g., z-transformations) from
previous studies
Sampling error
minimum amount of data such that the same results on
repeated trials
34. The Rockefeller Foundation gave grants for urban topics:
To Kevin Lynch (MIT) for studies of urban aesthetics
(Image of the City in 1960)
To Jane Jacobs for studies of urban life
(The Death and Life of Great American Cities in 1961)
35. The Death and Life of Great American Cities
the most influential book in city planning
(“social capital", "mixed primary uses", "eyes on the street”)
critique of the 1950s urban renewal policies
(attacking Moses for “replacing well-functioning neighborhoods
with Le Corbusier-inspired towers”)
36. Death caused by elimination of pedestrian activity
(highway construction, large-scale development projects)
Life meant pedestrians at all times of the day
(“sidewalk ballet”)
37. nothing is safer than a city
street that everybody uses
“the eyes on the street”
39. “At night, street crimes are most prevalent in places where
there are too few pedestrians to provide natural surveillance,
but enough pedestrians to make it worth a thief’s while”
54. ●
●
●
●
●
● ●
●
● ●
● ●
● ● ●
●
●
● ●
●
0.0
0.1
0.2
0.3
0 50 100 150 200
number of Flickr users per street
r(safety,age)
55. Crime prevention through environmental design
The physical environment can be designed or
manipulated to reduce fear of crime (by
supporting certain activities over others)
56. Questions 3 & 4
Can safe (walkable) streets be identified by the
presence of specific types of places?
57. To test the extent to which safety is associated with the pres-
enceof specific places, webuild alinear model that predicts safety
scores from the presence of first-level Foursquare categories. That
is, astreet’spredicted safety scoreiscomputed from thefraction of
places on it that fall into thedifferent categories:
saf etyi = ↵+β1 ar ts+β2 college+β3 f ood+β4 nightlif e+
β5 outdoor s + β6 residential + β7 shopping, +β8 tr avel + e.
It turnsout that theregression showsanadjusted R2
of 74%, sug-
gesting that safety can be accurately predicted only from the pres-
6
58. R2
= 74% (safety from crime)
safe streets: outdoor places (mainly parks)
unsafe ones: residential bits of central London that have no parks
59. R2
= 33% (walkability)
the presence of residential areas drives most
of the predictive power of the regression
60. Text
we gather the literature on walkability to
produce a list of walkability-related keywords
Line-by-line coding
1.Collecting documents
2.Annotating them
3.Validating them
64. To sum up...
Picture uploads from dwellers of walkable streets
differ from those of unwalkable ones, mainly in
terms of upload time and tagging *
* limited data vs. high penetration
65. Theoretical Implication
Social media = Opportunities for Theory
Comforted by our validation work, urban researchers might
well be enticed to use social media to answer theoretical
questions that could not have been tackled before because of
lack of data