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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

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