network, placemaking and sustainability · cities less safe cities total node density 106 per sq....

Network, Placemaking and Sustainability

Norman W. Garrick

Wesley Marshall

1945 1965 1985 2005

Norman W. Garrick

Vehicle Miles Traveled 1945 to 2005

Norman W. Garrick

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Miles per day per capita

1945 and 2008

5

13

20

27

0

10

20

30

1945 1965 1985 2005

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

Traffic Fatality (per 100,000)

Norman W. Garrick

0

10

20

30

1970 1980 1990 2000 2010

USA

The Netherlands

Davis, California

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

Davis

1940 1950 1960 1970 1980 1990 2000

Turlock

1940 1950 1960 1970 1980 1990

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

How Do we Characterize

Street Networks?

Gridded

Sparse Connected

Hierarchical

Dense

Intersection Density

Street Length

Connected Nodes

Characterizing Street Networks

• Street Network Configuration

• Street Network Scale

MACRO NETWORK

M

ICRO

NETW

ORK

Linear Tree

Grid Tributary Radial

Grid

Tre

e

PALO ALTO

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

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%

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%

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%

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

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

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

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

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 =

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)

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

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

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)

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”

Making Savannah

(http://ocw.mit.edu/ans7870/11/11.001j/f01/lectureimages/3/image24.html)