Andy Mortenson-Measuring Transportation Connectivity by RDI
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The document summarizes a 2009 transportation summit held in Portland, Oregon that discussed various transportation, land use, and sustainability policy issues. It introduced the Route Directness Index (RDI) as a new metric for measuring street and path connectivity. The RDI calculates the directness of routes between locations by dividing straight-line distances by actual travel distances. A higher RDI indicates better connectivity. The document provided examples of how the RDI could be used to evaluate existing connectivity, compare connectivity with and without new paths or streets, and prioritize transportation projects.
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Andy Mortenson-Measuring Transportation Connectivity by RDI
- 1. 2009 Transportation Summit – Portland, Oregon measuring Transportation Connectivity by Route Directness Index using * * Trademarks provided under license from ESRI.
- 2. Background Policy Issues Cities are looking at a host of transportation, land use, energy, environmental and sustainability policy issues and considering new measurement techniques: Z Complete Streets Policy Z Concurrency Program Refinements Z VMT and GHG per Capita Reduction Z Multi-Modal Level-of-Service (LOS) Z Street Connectivity Policies Connectivity between new/existing developed lands Non-motorized public accessways and limiting cul-de-sacs Grid-based standards for streets (500 feet ) and Non-motorized (330 feet) – emphasis on smaller block lengths Developing connectivity metrics
- 3. Testing Connectivity Metrics 1950’s Grid Network 1990’s Hierarchical Network A B A B C D C D 1990’s Hierarchical Network 261 / 146 = 1.79 Link / Node Ratio 158 / 143 = 1.10 107 Intersection Density 93 40 % % 4-Way Intersections 20 % .74 Route Directness Ratio .44 0.4 (Miles on Perimeter Arterial) 2.7 Connectivity measurements in small subareas are straight- forward; but what about city-wide?
- 4. Achieving VMT per Capita Reduction 0 Research % Change in Person Miles Travelled -5 conducted in Seattle area by C. -2% Lee and Anne -10 Moudon (University of DESIGN Washington), -15 Average Block Size 2006: Quantifying % 4-Way Intersections Land Use and -4% % Sidewalk Coverage Urban Form -20 Correlates of - 5% Walking -25 Residential Office Park Retail / Service Land Density Land Use Diversity Design Measures of connectivity help indicate transportation-efficient land uses that yield lower VMT and GHG per capita
- 5. Intersection Density Intersection Density 4-Way Intersection Density GIS mapping techniques can illustrate city-wide measures of intersection density but have difficulty illustrating “Plan” benefits Link-Node, Intersection Density and Walkscore Measures are only Proxies for connectivity – RDI is a direct measure of connectivity
- 6. Composite Accessibility Indices Can help identify and prioritize plans, but miss the important measure of system connectivity and notable gaps.
- 7. Defining RDI Z Define Route Directness Index Z The Route Directness Index (RDI) can be used to quantify how well a street network connects destinations. Z The RDI can be measured separately for motorized and non-motorized travel, taking into account non-motorized shortcuts, such as paths that connect cul-de-sacs, and barriers such as highways and streets that lack sidewalks. Z The RDI is calculated by dividing direct travel distances by actual travel distances. For example, if streets are connected, have good sidewalks, and blocks are relatively small, people can travel nearly directly to destinations, resulting in a high index. If the street network has many unconnected dead-ends and blocks are large, people must travel farther to reach destinations, resulting in a low index.
- 8. RDI Credits Z Jennifer Dill, Portland State University Research – Connectivity Metrics Z Victoria Transport Policy Institute Policy – Connectivity Metrics Z Charlier & Associates & Otak Intl. – CNU Practice Z Others
- 9. RDI Example: Pre Neighborhood Connector Route Directness Index Crow Flight 375 ft 1850 ft / Walk Distance 1850 ft RDI: .20 = RDI .20 375 ft Existing Shared-Use Path Route Directness Index can better illustrate “before- and-after” Plan improvements
- 10. RDI Example: Post Neighborhood Connector Route Directness Index Crow Flight 375 ft / Walk Distance 450 ft New RDI: .83 Neighborhood = Connectors RDI .83 375 ft 450 ft Existing Shared-Use Path Route Directness Index can better illustrate “before- and-after” Plan improvements
- 11. RDI – GIS Focal Exam Good Poor Testing RDI on a larger, city-wide scale is the challenge
- 12. Examples Using RDI DesktopTM X Bike Access to LRT Station Z Neighborhood Design / Growth Management Z Access to Commuter Rail Station Non-Motorized Concurrency and Quality of Service Z Pedestrian Access to LRT Station
- 13. Growth Management: Non-Motorized Concurrency and Quality of Service Using RDI Desktop to 1 demonstrate functional implementation of a Master Plan area: • Measuring connectivity with & without exclusive pedestrian routes Z RDI Measure: Neighborhood Connectivity
- 14. Planned Neighborhood Z Neighborhood design: Mixture of villa plot size Neighborhood centers Z Maximized public realm for non- motorized connectivity through: Quality street pedestrian zone Connecting exclusive pedestrian routes, and park/open spaces
- 15. Neighborhood RDI Score Z Measured without Pedestrian connections Z Fair RDI scores RDI DesktopTM Metric Poor Fair Parcel Parcel Excellent Average RDI Score: Fair .65
- 16. Neighborhood RDI Score Z Measured with Pedestrian connections Z Good-Excellent RDI scores RDI DesktopTM Metric Poor RDI scoring can be used to establish non- Fair motorized concurrency measures and Excellent thresholds, used to evaluate future land development plans for policy compliance Parcel Parcel Average RDI Score: Good .73
- 17. Comparative RDI Scoring Z RDI Score Difference: With and Without Pedestrian connections RDI DesktopTM Metric Parcel Parcel Plots that benefit significantly by Pedestrian connectivity
- 18. Intersection Density Scoring Z Intersection Density Score Without SUPs Poor Fair Excellent Average Density Score: Poor 68
- 19. Intersection Density Scoring Z Intersection Density Score With SUPs Poor Fair Excellent Average Density Score: Good 142
- 20. Link-Node Scoring Z Node-Link Score Without SUPs Link-Node Ratio: 1.66
- 21. Link-Node Scoring Z Node-Link Score With SUPs Link-Node Ratio: 1.67
- 22. Seattle’s Mt. Baker Link LRT Station Example Z RDI Measure: Pedestrian Access to LRT Station
- 23. Establish GIS Database Z Study area Z Light rail line Z Street centerline Z Parcel data
- 24. Create Pedestrian Network Z Create Pedestrian Network Z Illustrate Importance of “Hanford Steps”
- 25. Calculate Base Year RDI Z Study Parcels (2,000 foot radius buffer from LRT station) Z Pedestrian RDI to Mt. Baker Station Z Baseline Conditions (assumes no Hanford Steps) Z RDI Average = 0.67 RDI DesktopTM Metric Poor Parcel Station Good Average RDI Score: Fair .67
- 26. Calculate PMP RDI Z Pedestrian RDI to Mt. Baker Station Z RDI Impact of Hanford Steps RDI DesktopTM Metric Poor Parcel Station Good Average RDI Score: Good .72
- 27. Estimate RDI Enhancement Z Pedestrian RDI to Mt. Baker Station Z Difference between Baseline RDI and Hanford Steps RDI Z Baseline: 58% of parcels above RDI 0.65 threshold. Z Steps RDI: 73% of parcels above threshold. Z Additional 40 more parcels. RDI scoring can be used to sharpen plan priorities, particularly as federal and state funding becomes more competitive
- 28. Intersection Density Z Without link Z Average: 296 intersections per mi2 Poor Good Average Density Score: Fair 296
- 29. Intersection Density Z With project Z Average: 302 intersections per mi2 Z Marginal increase Poor Good Average Density Score: Fair 302
- 30. Comparing Station Area Scores Baseline Sidewalk Project Improvement Average Score Average Score Increased Connectivity RDI - .67 RDI - .72 7.5 % Increase Improved Connectivity for 52 residential lots Measured Connectivity Between Route Directness Land Parels and LRT Station Index Poor Poor Good Good Int / Sq Mi - 296 Int / Sq Mi - 302 2 % Increase Intersection Density Not Available Poor Poor Good Good
- 31. Seattle’s Beacon Hill Link LRT Station Example X RDI Measure: Bike Access to LRT Station
- 32. Import GIS Database X Study area X Light rail line X Street centerline X Parcel data
- 33. Create Bicycle Network X Create bike network X Bicycle Master Plan – existing conditions (2004)
- 34. Route Choice Analyses X Route Directness Index X Weighted Distance based on bicycle network characteristics Weighted Distance = Distance / [ [ x * (0.80) + y * (0.20)] * (0.10) ] Impedance where Bike Facility Type (FT) Score (x) SDOT Code Shared-Use Path 10 9, 23 Bike Boulevard 9.5 8 Bike Lane (both sides) 8 1, 16 Bike Lane (one side) 6 2, 19 Sharrow 5 3, 14 Shared Lane 5 30, 40 Shared (arterial) 2 10 Shared (other) 0 15, 21, 77 Slope and Slope Score (y) <2% 10 2-4% 8 4-8% 5 8 -12 % 3 > 12 % 0
- 35. Calculate Base Year RDI X Study parcels (one- mile link distance) X Routes from parcels to Beacon Hill Station X Existing Conditions (2004) Poor Good
- 36. Calculate BMP RDI X Added Bike Lanes noted in Bicycle Master Plan (BMP) Poor Good
- 37. Estimate RDI Enhancement X Difference between Existing RDI and BMP RDI
- 38. Alternatives Analysis X Testing new Bicycle Boulevard project to improve E-W connectivity RDI scoring can be used to identify BMP oriented mostly supplemental master plans, using north-south (arterials)… Poor detailed route-choice analyses that …instead of to LRT sta. integrate walkability and bicycle Good compatibility indices
- 39. RDI Comparison X Difference between BMP RDI and RDI with added Bike Boulevard project
- 40. Connectivity to LRT Bicycle System Connectivity Scores Poor Poor Good Good Baseline Measure: Plan Refinement: Project Impact: Bicycle Master Plan New Bicycle Boulevard Improved Connectivity
- 41. Non-motorized System Plan Evaluation Z RDI Measure: Pedestrian Network Connectivity
- 42. Existing Conditions Shared-Use Path Connections Average RDI Score: Poor / Fair .58
- 43. New Shared-Use Paths Shared-Use Path Connections Average RDI Score: Fair / Good .66 14 % improvement
- 44. RDI – “Before & After” Sensitive to Block Length Shared-Use Path Connections Sensitive to Cul-de- Sac Length RDI scoring is sensitive to urban design principles – because it directly measures connectivity 305 ft 330ft
- 45. RDI – “Before & After” Delta Shared-Use Path Connections
- 46. Link-Node: Before Shared-Use Path Connections Nodes 74 Links 107 Ratio 1.45 Link-Node Ratio: 1.45
- 47. Link-Node: After Shared-Use Path Connections Nodes 92 Links 141 Ratio 1.53 Link-Node Ratio: 1.53 5.5 % improvement
- 48. Lakewood Sounder Commuter Rail Station Example Z RDI Measure: Access to Commuter Rail Station
- 49. Lakewood’s NMTP RR Over-crossing New Pedestrian-Bicycle Connections Lakeview Ave. 111th Street 112th Street Bridgeport Way St Claire Hospital Option A Option B 115th Street Non-Motorized Improvement Options Shared-Use Path 47th Avenue Bike Lanes & Sidewalks Bike Lanes "Sharrow" - Shared-Lane Non-Motorized Railroad Overpass I-5 Overpass Retrofit / Bike Lanes and Sidewalks Sounder Commuter Rail I-5 Over-crossing
- 50. RDI - Baseline Z Testing RDI: Land Use – to Sounder Station Z Land Use (building structures) within One-Mile Radius Z “Baseline” = Existing Pedestrian System Connectivity Poor Fair Good
- 51. RDI – After I-5 Crossing Z Impact of I-5 Over-Crossing Improvements Z Addition of Sidewalks and Bike Lanes Poor Fair Good
- 52. RDI – After RR Crossing Z Impact of New Railroad Over-Crossing Z Exclusive Non-Motorized Facility Poor Fair Good
- 53. Why Use Route Directness Index Z RDI metric can enumerate important quality of connectedness, a primary factor (along with land mix and density) in urban transportation sustainability by: Directly measuring street / pathway connections, rather than proxy measures, and Mapping spatial variation in land use connectivity Z RDI calculates numerical metrics to evaluate the quality of a connection between an origin location and one or more destinations. These metrics can be mapped thematically at the origin location to highlight areas of connectivity quality (range, good-bad). Z Using these metrics, before and after analyses can be performed to quantify and locate the impacts of improved connections (especially non-motorized connections), establishing Comparative RDI Benefit to Existing Land Use
- 54. Route Choice Modeling Z Non-motorized system quality, or levels and types of obstacles (impedances) are important factors to consider in walking and cycling route choice sub- models
- 55. How Can RDI DesktopTM Help? Z Street Design Policy Implementation – measurable guidelines Z Establish Non-motorized Neighborhood Connectivity Standards Design guide thresholds for neighborhood planning site plan review – non- motorized concurrency Z Non-Motorized Plan Strategic Prioritization Measure current networks - target critical non-motorized connections Minimizing expensive and unnecessary data collection Help expedite Draft Non-motorized Plan project identification and priorities Consistently evaluate and rank multi-modal projects for federal Transportation Enhancement Program grant applications Z Critical Plan Priority Analysis and Ranking – consistent and robust technique (with other sub-models) to measure important: Neighborhood Connectors Transit Access Connectors Urban Boulevard Crossings
- 56. Contact Andy Mortensen * WHAT TRANSPORTATION CAN BE andy.mortensen@transpogroup.com 503.313.6946 www.transpogroup.com Abu Dhabi | Kirkland | Seattle | Boise * Trademarks provided under license from ESRI.