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Utilizing GIS to Measure Street Connectivity

and Pedestrian Accessibility

Comparing Cul-De-Sac and Grid Neighborhoods

in the Houston Metropolitan Area

GIS-Transportation Symposium

Chang Yi

Community & Regional Planning

University of Texas at Austin

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Presentation Outline

Background

Research Question Neighborhood Selections & Descriptions

Analysis Methods

Findings

Conclusions & Implications

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Background |Research Questions | Neighborhoods | Analytic Methods | Findings | Conclusions & Implications

What is Connectivity / Accessibility?

Street Connectivity

The Level of Inter-Connectedness of Streets

Pedestrian Accessibility The Level of Ease in reaching Spatially Separate

Opportunities (by walking) Travel Distance

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Background |Research Questions | Neighborhoods | Analytic Methods | Findings | Conclusions & Implications

Why Connectivity and Accessibility?

New Urbanists

Cul-De-Sac (-)

Streets not Inter-Connected

Few Route Choices Long Dist.

Discourage Peds/Auto.Dependence Specialized Functions: Inefficient

Traffic Congestion in Major Roads

Grid (+)

Highly connected Streets

More Route Choices

Shorter Distances Easier for Pedestrian Travels

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Background |Research Questions | Neighborhoods | Analytic Methods | Findings | Conclusions & Implications

Why not?

Developers/Homebuyers Grid (-)

Through traffics (Crane, 1996) Nuisance: Safety Hazards, Noise

Increase Infra. Cost

(holding all other things equal)

Decrease Affordability/Profitability

Cul-De-Sac (+)

No Through Traffics

Quiet / Private Residential Env.

Safer (for children) Market Preference toward Cul-De-Sac

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Background |Research Questions | Neighborhoods | Analytic Methods | Findings | Conclusions & Implications

Grid Street converted to Cul-De-Sac, City of Berkeley

Source: Southworth and Ben-Joseph, 2004

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Background |Research Questions | Neighborhoods | Analytic Methods | Findings | Conclusions & Implications

Alternative Street Design?

Creative Cul-De-Sacs ?

(Southworth and Ben-Joseph, 2004) Cul-De-Sacs integrated with Open Space and Local

Destinations on Ped-Friendly Environment

Cul-De-Sac Neighborhoods with High Street

Connectivity and Accessibility + Benefits of CDS

Not Streets, Pedestrian-Oriented Design Street Debate may have overlooked the Importance of

Neighborhood Design and misses Potentials of CDS

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Background |Research Questions | Neighborhoods | Analytic Methods | Findings | Conclusions & Implications

Any Example of

Creatively Designed Cul-De-Sac?

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Source: Stein, 1966

Background |Research Questions | Neighborhoods | Analytic Methods | Findings | Conclusions & Implications

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Source: Stein, 1966

Background |Research Questions | Neighborhoods | Analytic Methods | Findings | Conclusions & Implications

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Background |Research Questions | Neighborhoods | Analytic Methods | Findings | Conclusions & Implications

Radburn: Creatively Designed Cul-De-Sacs

Short & Straight Cul-De-Sacs

Auto-Oriented (separated from Pedestrians)

Private and Quiet Residential Environments

Benefits of Cul-De-Sacs

Connect Pedestrian Movement with Natural

Features and Local Destinations

Schools / Parks are Accessible for Pedestrians

Benefits of the Grid

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Background |Research Questions | Neighborhoods | Analytic Methods | Findings | Conclusions & Implications

Research Question

Could the benefits New Urbansits try to achieve

with a grid street pattern be realized in a cul-de-sac

oriented neighborhood?

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Background |Research Questions | Neighborhoods | Analytic Methods | Findings | Conclusions & Implications

Neighborhood Selection

The Radburn-Influenced Neighborhood

Grand Lakes, Katy

Pure Grid Street Neighborhood

Houston Heights, Houston Conventional Cul-De-Sac Neighborhood

The Panther Creek Village, The Woodlands

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Background |Research Questions | Neighborhoods | Analytic Methods | Findings | Conclusions & Implications

Case 1: Hybrid Cul-De-Sac

Grand Lakes

Radburn-Influenced Cul-De-Sac +

Pedestrian Trails

1,400 acre

Parks

Elementary Schools

Clear boundary

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Background |Research Questions | Neighborhoods | Analytic Methods | Findings | Conclusions & Implications

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Pedestrian Trail

Lake

Elementary School

Park

Background |Research Questions | Neighborhoods | Analytic Methods | Findings | Conclusions & Implications

N i hb h d

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Case 2: Pure Grid

Houston Heights

Downtown Historic District

1,500 Acre

Schools, PocketParks, Community

Centers

Background |Research Questions | Neighborhoods | Analytic Methods | Findings | Conclusions & Implications

B k d |R h Q i | N i hb h d | A l i M h d | Fi di | C l i li i

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Background |Research Questions | Neighborhoods | Analytic Methods | Findings | Conclusions & Implications

The Panther Creek

Village, the Woodlands

Ian McHarg

Ecological Planning

Conventional Cul-

De-Sacs

1,700 acre

Boundary defined by

Major Arterials

Case 3: Conventional Cul-De-Sacs

B k d |R h Q i | N i hb h d | An l i M th d | Fi di | C l i & I li i

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Background |Research Questions | Neighborhoods |Analysis Methods | Findings | Conclusions & Implications

Measuring Street Connectivity & Pedestrian Accessibility

Street Connectivity Indicators

Link Node Ratio

Percentage of Cul-De-Sacs

Percentage of 4 way Intersections

Street Density(Total Street Miles/Neighborhood Area)

Alpha Index / Gamma Index

Pedestrian Accessibility Indicators

Pedestrian Route Directness (PRD)

Pedestrian Catchment Area (PCA)TransCAD GIS

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Street Connectivity: Link Node Ratio

Internal Street Connectivity

intersections / intersections + cul-de-sacs

Three

routes

Link Node Ratio = 7/8 = 0.88

Only One Route from A to B

A

B

Three Routes from A to B

Link Node Ratio = 9/8 = 1.13

Source & Presentation Idea : Dill, 2004

Ratio = 7/8 = 0.88

A

B

Ratio = 7/8 = 0.88

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= Network Area/Aerial Area

(Always Smaller than 1)

Pedestrian Catchment Area

(PCA)

A Quarter Mile Network Buffer

A Quarter Mile Aerial Buffer

P d i R Di

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a1 a2 a3

a4

a5

PARK

Pedestrian Route Directness

(Without Ped Trail)

Aerial Distancea1+a2+a3+a4+a5++aN = A

b1 b2 b3

b4b5

PARK

Shortest Network Distance

b1+b2+b3+b4+b5++bN = B

PRD for Park = Net/Aerial Dist.

=B/A (>1)

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a1 a2 a3

a4

a5

PARK

Pedestrian Route Directness

(with Pedestrian Trail)

Aerial Distancea1+a2+a3+a4+a5++aN = A

PARK

c1 c2 c3

c4

c5

Shortest Network Distance

c1+c2+c3+c4+c5++cN = C

PRD for Park = Net/Aerial Dist.

=C/A (>1)

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How to Measure Street Connectivity?

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Digitizing Neighborhood Map

Di i i i i hb h d M

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Digitizing Neighborhood Map

Di i i i N i hb h d M

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Digitizing Neighborhood Map

Background |Research Questions | Neighborhoods | Analytic Methods | Findings | Conclusions & Implications

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Findings: Street ConnectivityGrand

Lakes

No Trails

Grand Lakes

With Trails

Panther

Creek

Village

Houston

Heights

Street Pattern ConventionalCul-De-Sacs

HybridCul-De-Sacs

Cul-De-Sacs

Grid

Link Node Ratio1.11 1.38 1.10 1.65

Percentage of Cul-De-Sacs 0.39 0.14

0.41 0.03

Percentage of 4

Way Intersections 0.06 0.100.08

0.82

Street Density

(Miles/Area) 16.00 22.23 17.32 22.72

Alpha Index

0.06 0.19 0.05 0.33Gamma Index

0.37 0.46 0.37 0.55

Background |Research Questions | Neighborhoods | Analytic Methods | Findings | Conclusions & Implications

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Findings: Street ConnectivityGrand

Lakes

No Trails

Grand Lakes

With Trails

Panther

Creek

Village

Houston

Heights

Street Pattern ConventionalCul-De-Sacs

HybridCul-De-Sacs

Cul-De-Sacs

Grid

Link Node Ratio1.11 1.38 1.10 1.65

Percentage of Cul-De-Sacs 0.39 0.14

0.41 0.03

Percentage of 4

Way Intersections 0.06 0.100.08

0.82

Street Density

(Miles/Area) 16.00 22.23 17.32 22.72

Alpha Index

0.06 0.19 0.05 0.33Gamma Index

0.37 0.46 0.37 0.55

Background |Research Questions | Neighborhoods | Analytic Methods | Findings | Conclusions & Implications

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Findings: Street ConnectivityGrandLakes

No Trails

Grand Lakes

With Trails

Panther

Creek

Village

Houston

Heights

Street Pattern ConventionalCul-De-Sacs

HybridCul-De-Sacs

Cul-De-Sacs

Grid

Link Node Ratio1.11 1.38 1.10 1.65

Percentage of Cul-De-Sacs 0.39 0.14

0.41 0.03

Percentage of 4

Way Intersections 0.06 0.100.08

0.82

Street Density

(Miles/Area) 16.00 22.23 17.32 22.72

Alpha Index

0.06 0.19 0.05 0.33Gamma Index

0.37 0.46 0.37 0.55

Background |Research Questions | Neighborhoods | Analytic Methods | Findings | Conclusions & Implications

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Findings: Street ConnectivityGrand

Lakes

No Trails

Grand Lakes

With Trails

Panther

Creek

Village

Houston

Heights

Street Pattern ConventionalCul-De-Sacs

HybridCul-De-Sacs

Cul-De-Sacs

Grid

Link Node Ratio1.11 1.38 1.10 1.65

Percentage of Cul-De-Sacs 0.39 0.14

0.41 0.03

Percentage of 4

Way Intersections 0.06 0.100.08

0.82

Street Density

(Miles/Area) 16.00 22.23 17.32 22.72

Alpha Index

0.06 0.19 0.05 0.33Gamma Index

0.37 0.46 0.37 0.55

Background |Research Questions | Neighborhoods | Analytic Methods | Findings | Conclusions & Implications

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Findings: Street ConnectivityGrand

Lakes

No Trails

Grand Lakes

With Trails

Panther

Creek

Village

Houston

Heights

Street Pattern ConventionalCul-De-Sacs

HybridCul-De-Sacs

Cul-De-Sacs

Grid

Link Node Ratio1.11 1.38 1.10 1.65

Percentage of Cul-De-Sacs 0.39 0.14

0.41 0.03

Percentage of 4

Way Intersections 0.06 0.100.08

0.82

Street Density

(Miles/Area) 16.00 22.23 17.32 22.72

Alpha Index

0.06 0.19 0.05 0.33Gamma Index

0.37 0.46 0.37 0.55

Background |Research Questions | Neighborhoods | Analytic Methods | Findings | Conclusions & Implications

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Summary of Findings: Street Connectivity

Among the Selected Neighborhoods:

The Highest in the Grid Neighborhood

Higher in Hybrid Cul-De-Sac than the

Conventional Cul-De-Sac

Street Density for Hybrid is higher thanConventional Cul-De-Sac & Comparable with

the Grid

Leading to Higher Cost for Development

Background |Research Questions | Neighborhoods | Analytic Methods | Findings | Conclusions & Implications

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Findings: Pedestrian Accessibility for Parks

Accessibility for Parks

Aggregated

AerialDistance

Aggregated

NetworkDistance

PRD PCA

Grand Lakes withPed. Trails

Parks (6)0.86 1.30 1.51 0.38

Grand Lakes withoutPed.

Trails

Parks (6)

0.86 1.36 1.58 0.21

Houston Heights

Parks (10)1.10 1.57 1.65 0.51

The Panther Creek VillagePark (8) 0.94 1.45 1.54 0.22

(The Lower the PRD / The Higher the PCA Higher Accessibility)

Background |Research Questions | Neighborhoods | Analytic Methods | Findings | Conclusions & Implications

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Findings: Pedestrian Accessibility for Parks

(The Lower the PRD / The Higher the PCA Higher Accessibility)

Accessibility for Parks

Aggregated

AerialDistance

Aggregated

NetworkDistance

PRD PCA

Grand Lakes withPed. Trails

Parks (6)0.86 1.30 1.51 0.38

Grand Lakes withoutPed.

Trails

Parks (6)

0.86 1.36 1.58 0.21

Houston Heights

Parks (10)1.10 1.57 1.65 0.51

The Panther Creek VillagePark (8) 0.94 1.45 1.54 0.22

Background |Research Questions | Neighborhoods | Analytic Methods | Findings | Conclusions & Implications

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Findings: Pedestrian Accessibility for Parks

(The Lower the PRD / The Higher the PCA Higher Accessibility)

Accessibility for Parks

Aggregated

AerialDistance

Aggregated

NetworkDistance

PRD PCA

Grand Lakes withPed. Trails

Parks (6)0.86 1.30 1.51 0.38

Grand Lakes withoutPed.

Trails

Parks (6)

0.86 1.36 1.58 0.21

Houston Heights

Parks (10)1.10 1.57 1.65 0.51

The Panther Creek VillagePark (8) 0.94 1.45 1.54 0.22

Background |Research Questions | Neighborhoods | Analytic Methods | Findings | Conclusions & Implications

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Findings: Pedestrian Accessibility for Schools

(The Lower the PRD / The Higher the PCA Higher Accessibility)

Accessibility for Schools

Aggregated

AerialDistance

Aggregated

NetworkDistance

PRD PCA

Grand Lakes withPed. Trails

Schools (2)1.06 1.47 1.39 0.31

Grand Lakes withoutPed.

Trails

Schools (2)

1.06 1.56 1.47 0.13

Houston Heights

Schools (11)1.05 1.36 1.31 0.52

The Panther Creek Village

Schools (2)0.89 1.30 1.46 0.34

Background |Research Questions | Neighborhoods | Analytic Methods | Findings | Conclusions & Implications

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Findings: Pedestrian Accessibility for Schools

(The Lower the PRD / The Higher the PCA Higher Accessibility)

Accessibility for Schools

Aggregated

AerialDistance

Aggregated

NetworkDistance

PRD PCA

Grand Lakes withPed. Trails

Schools (2)1.06 1.47 1.39 0.31

Grand Lakes withoutPed.

Trails

Schools (2)

1.06 1.56 1.47 0.13

Houston Heights

Schools (11)1.05 1.36 1.31 0.52

The Panther Creek Village

Schools (2)0.89 1.30 1.46 0.34

Background |Research Questions | Neighborhoods | Analytic Methods | Findings | Conclusions & Implications

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Findings: Pedestrian Accessibility for Retails

(The Lower the PRD / The Higher the PCA Higher Accessibility)

Accessibility for Retails

Aggregated

AerialDistance

Aggregated

NetworkDistance

PRD PCA

Grand Lakes withPed. Trails

Retails (3)0.80 1.18 1.48 0.21

Grand Lakes withoutPed.

Trails

Retails (3)

0.80 1.27 1.59 0.12

Houston Heights

Retails (0)N/A N/A N/A N/A

The Panther Creek Village

Retails (1)0.91 1.28 1.41 0.20

Background |Research Questions | Neighborhoods | Analytic Methods | Findings | Conclusions & Implications

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Findings: Pedestrian Accessibility for Retails

(The Lower the PRD / The Higher the PCA Higher Accessibility)

Accessibility for Retails

Aggregated

AerialDistance

Aggregated

NetworkDistance

PRD PCA

Grand Lakes withPed. Trails

Retails (3)0.80 1.18 1.48 0.21

Grand Lakes withoutPed.

Trails

Retails (3)

0.80 1.27 1.59 0.12

Houston Heights

Retails (0)N/A N/A N/A N/A

The Panther Creek Village

Retails (1)0.91 1.28 1.41 0.20

Background |Research Questions | Neighborhoods | Analytic Methods | Findings | Conclusions & Implications

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Summary of Findings: Pedestrian Accessibility

Among the Selected Neighborhoods:

Ped. Catchment Area is the highest in the Grid

Between Grid and Cul-De-Sac:

In terms of PRD, Higher Accessibility in the Grid

Between Cul-De-Sac neighborhoods:Mostly, Hybrid CDS > Conventional CDS

High Accessibility to Retails in Conventional CDS Reinforcing the Importance of Neighborhood

Design

Background |Research Questions | Neighborhoods | Analytic Methods | Findings | Conclusions & Implications

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Conclusions and Implications

Implications?

Market appreciates Pedestrian Friendly Features in

Suburban Neighborhoods -> Recognizing the Demand This Preference is Expressed in Different Way

Integrate Cul-De-Sacs with Ped. Oriented Features

Walkability Benefits Outweighed Dev. Costs

Radburn as an Old Wisdom ? (Lee and Ahn, 2003)

Might be Politically & Physically More Feasible Alt. Types of Streets Neighborhood Design

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Thank you very much

Question?

Chang Yi

Community and Regional PlanningUniversity of Texas at Austin