network, placemaking and sustainability · cities less safe cities total node density 106 per sq....
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Network, Placemaking and Sustainability
Norman W. Garrick
Wesley Marshall
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1945 1965 1985 2005
Norman W. Garrick
Vehicle Miles Traveled 1945 to 2005
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Norman W. Garrick
You are here
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Miles per day per capita
1945 and 2008
5
13
20
27
0
10
20
30
1945 1965 1985 2005
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0.0
10.0
20.0
30.0
Norman W. Garrick
The Transportation Sustainability Gap
Sustainability Gap
USA
Norway
Daily Miles Traveled For every man,
woman and child
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Traffic Fatality (per 100,000)
Norman W. Garrick
0
10
20
30
1970 1980 1990 2000 2010
USA
The Netherlands
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Davis, California
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24 California Cities
Alameda Berkeley
Chico
Cupertino
Danville
Davis
La Habra
Palo Alto
San Luis Obispo
San Mateo
Santa Barbara
Santa Cruz
Antioch Apple Valley
Carlsbad
Madera
Morgan Hill
Perris
Redding
Rialto
Temecula
Turlock
Victorville
West Sacramento
Safe
r Cit
ies
Less
Safe
Cit
ies
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Davis
1940 1950 1960 1970 1980 1990 2000
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Turlock
1940 1950 1960 1970 1980 1990
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CALIFORNIA CITY COMPARISON
Safer Cities
Less Safe Cities
Mode Share
Population 65,719 59,845
Driving 84.1% 95.8%
Population Density
5,736 per sq. mi. 2,673 per sq. mi.
Intersection Density
106 per sq. mi. 63 per sq. mi.
Walking 5.4% 1.7%
Biking 4.1% 0.7%
Transit 6.6% 1.7%
Road Fatalities
per 100,000 population
3.2 per year 10.5 per year
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How Do we Characterize
Street Networks?
Gridded
Sparse Connected
Hierarchical
Dense
Intersection Density
Street Length
Connected Nodes
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Characterizing Street Networks
• Street Network Configuration
• Street Network Scale
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MACRO NETWORK
M
ICRO
NETW
ORK
Linear Tree
Grid Tributary Radial
Grid
Tre
e
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PALO ALTO
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Linear Tree
Grid Tributary Radial
Grid
Tre
e
NETWORK COMPARISON
Avg. Year of
Development 1965 1974 1966 1966
Avg. Year of
Development 1950 Pre 1940 Pre 1940
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Linear Tree
Grid Tributary Radial
Grid
Tre
e
Safer Cities
Less Safe Cities
NETWORK COMPARISON
5%
6%
40%
30%
2%
15%
21%
34%
Safer Cities
Less Safe Cities
N/A
N/A
4%
5%
3%
1%
25%
9%
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NODE COMPARISON
Safer Cities
Less Safe Cities
Total Node Density
106 per sq. mi. 63 per sq. mi.
Dead End Node Density 32 per sq. mi. 23 per sq mi.
% Dead Ends 30.2% 36.5%
LEED-ND Node Density
74 40
Macro & Intermediate
Node Density 6.9 per sq. mi. 5.2 per sq. mi.
% Major Nodes 6.3% 8.2%
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SAFETY COMPARISON
Safer Cities
Less Safe Cities
Fatal or Severe Crashes
12.7 per year 17.0 per year
Micro Road Fatal or Severe 2.0 per year 1.7 per year
% Fatal or Severe 1.7% 2.7%
Macro & Intermediate
Fatal or Severe 9.1 per year 13.7 per year
% Fatal or Severe 1.8% 3.3%
% Fatal or Severe 1.6% 3.1%
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LT GT
Node Density
Dead End Density
SAFER CITIES - NETWORK TYPE COMPARISON
105
42
155
42
185
33
195
39
Vehicle Mode Share
% Fatal or Severe
87.8%
2.9%
86.1%
2.8%
88.9%
1.7%
87.5%
2.0%
Node Density
Dead End Density
N/A
N/A
250
26
279
16
256
13
Vehicle Mode Share
% Fatal or Severe
N/A
N/A
84.9%
2.0%
79.4%
1.6%
70.8%
1.5%
(Non-HW Crashes)
RT TT
LG GG RG TG
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Node Density
Dead End Density
LESS SAFE CITIES - NETWORK TYPE COMPARISON
65
28
88
31
111
41
116
25
Vehicle Mode Share
% Fatal or Severe
95.5%
11.9%
94.5%
4.4%
95.5%
3.9%
94.9%
3.8%
Node Density
Dead End Density
N/A
N/A
158
12
N/A
N/A
201
10
Vehicle Mode Share
% Fatal or Severe
N/A
N/A
90.2%
2.6%
N/A
N/A
89.2%
2.4%
(Non-HW Crashes)
LT GT RT TT
LG GG RG TG
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SAFER CITIES – NETWORK DENSITY
Mode Share
Driving 88.1%
Network Density
Comparison
< 81
Walking 5.3%
Biking 2.4%
Transit 3.0%
% Fatal or Severe
4.9%
86.7%
81-144
3.9%
3.8%
4.5%
2.3%
82.9%
144-225
5.3%
4.0%
6.8%
1.8%
76.2%
225+
8.1%
4.2%
10.4%
2.0%
Intersection Density
9x9 12x12 15x15
Block Length 660’ 480’ 375’
1 Sq. Mile Grid Size
81 144 225
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LESS SAFE CITIES – NETWORK DENSITY
Mode Share
Driving 94.9%
Network Density
Comparison
< 81
Walking 2.1%
Biking 0.4%
Transit 1.4%
% Fatal or Severe
5.8%
95.0%
81-144
1.6%
0.6%
2.0%
3.3%
93.6%
144-225
2.1%
0.6%
2.3%
3.4%
89.4%
225+
4.9%
1.0%
2.8%
4.0%
Intersection Density
9x9 12x12 15x15
Block Length 660’ 480’ 375’
1 Sq. Mile Grid Size
81 144 225
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Nodes
HIGH CONNECTIVITY A DENSE NETWORK
9x9 12x12 15x15 Assuming a 1 Sq. Mile Grid
Links
Connectivity Index
144
81
264
144
420
225
1.78 1.83 1.87
Connectivity Index
= # of real intersections
# of real intersections + dead ends
Dead Ends
Real Intersections
Connected Node Ratio
81
0
144
0
225
0
1.0 1.0 1.0
Connected Node Ratio (CNR)
Link to Node Ratio =
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Radburn, New Jersey
American version of English Garden City
“Superblock” design
each block between 30 and 50 acres
One of the earliest American road hierarchies including cul-de-sacs
(Southworth & Ben-Joseph, 1997)
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Radburn Cul-de-sacs
(www.columbia.edu/cu/gsapp/projs
/call-it-home/html/chapter8.1.html)
(www.radburn.org/map3n.html)
“The flood of motors had already made the gridiron pattern, which had formed the framework for urban real estate for over a century, as obsolete as a fortified town wall.”
– Charles Stein, Radburn Designer
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Federal Housing Administration (FHA) created publications recommending specific street patterns
Endorsed hierarchical street layouts with cul-de-sacs that minimize
through traffic on residential streets
(www.columbia.edu/cu/gsapp/projs/call-it-home/html/chapter8.2.html)
Federal Housing Administration
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FHA called the grid layout:
monotonous,
with little character,
uneconomical,
and unsafe…
(www.columbia.edu/cu/gsapp/projs/call-it-home/html/chapter8.2.html)
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1938 - FHA Technical Bulletin No. 7 Planning Profitable Neighborhoods
“short blocks not
economical”
(www.columbia.edu/cu/gsapp/projs/call-it-home/html/chapter8.2.html)
We should
“discourage
through traffic”
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Making Savannah
(http://ocw.mit.edu/ans7870/11/11.001j/f01/lectureimages/3/image24.html)