CNU Summit 2009 RDI

measuring Transportation Connectivity by Route Directness Index using * * Trademarks provided under license from ESRI. 2009 Transportation Summit – Portland, Oregon

Background Policy Issues
Complete Streets Policy
Concurrency Program Refinements
VMT and GHG per Capita Reduction
Multi-Modal Level-of-Service (LOS)
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
Cities are looking at a host of transportation, land use, energy, environmental and sustainability policy issues and considering new measurement techniques:

Testing Connectivity Metrics
Link / Node Ratio
Intersection Density
% 4-Way Intersections
Route Directness Ratio
1990’s Hierarchical Network 1990’s Hierarchical Network 1950’s Grid Network A B C D A B C D 261 / 146 = 1.79 107 40 % .74 158 / 143 = 1.10 93 20 % .44 (Miles on Perimeter Arterial) 0.4 2.7 Connectivity measurements in small subareas are straight-forward; but what about city-wide?

Achieving VMT per Capita Reduction - 4 % - 2 % - 5% Measures of connectivity help indicate transportation-efficient land uses that yield lower VMT and GHG per capita Research conducted in Seattle area by C. Lee and Anne Moudon (University of Washington), 2006: Quantifying Land Use and Urban Form Correlates of Walking

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

Composite Accessibility Indices Can help identify and prioritize plans, but miss the important measure of system connectivity and notable gaps.

Defining RDI
Define Route Directness Index
The Route Directness Index (RDI) can be used to quantify how well a street network connects destinations.
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.
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.

RDI Credits
Jennifer Dill, Portland State University
Research – Connectivity Metrics
Victoria Transport Policy Institute
Policy – Connectivity Metrics
Charlier & Associates & Otak Intl. – CNU
Practice
Others

RDI Example: Pre Neighborhood Connector Route Directness Index can better illustrate “before-and-after” Plan improvements Existing Shared-Use Path Route Directness Index Crow Flight Walk Distance RDI / = 1850 ft 1850 ft RDI: .20 .20 375 ft 375 ft

RDI Example: Post Neighborhood Connector Route Directness Index can better illustrate “before-and-after” Plan improvements Existing Shared-Use Path Route Directness Index Crow Flight Walk Distance RDI = New Neighborhood Connectors / 375 ft 375 ft RDI: .83 .83 450 ft 450 ft

RDI – GIS Focal Exam Testing RDI on a larger, city-wide scale is the challenge Poor Good

Examples Using RDI Desktop TM
Access to Commuter Rail Station
Bike Access to LRT Station
Pedestrian Access to LRT Station
Neighborhood Design / Growth Management
Non-Motorized Concurrency and Quality of Service

Growth Management: Non-Motorized Concurrency and Quality of Service
Using RDI Desktop to demonstrate functional implementation of a Master Plan area:
Measuring connectivity with & without exclusive pedestrian routes
RDI Measure: Neighborhood Connectivity
1

Planned Neighborhood
Neighborhood design:
Mixture of villa plot size
Neighborhood centers
Maximized public realm for non-motorized connectivity through:
Quality street pedestrian zone
Connecting exclusive pedestrian routes, and park/open spaces

Neighborhood RDI Score
Measured without Pedestrian connections
Fair RDI scores
Poor Fair Excellent Parcel RDI Desktop TM Metric Parcel Average RDI Score: Fair .65

Neighborhood RDI Score
Measured with Pedestrian connections
Good-Excellent RDI scores
Poor Fair Excellent Parcel RDI Desktop TM Metric Parcel Average RDI Score: Good .73 RDI scoring can be used to establish non-motorized concurrency measures and thresholds, used to evaluate future land development plans for policy compliance

Comparative RDI Scoring
RDI Score Difference: With and Without Pedestrian connections
Parcel RDI Desktop TM Metric Parcel Plots that benefit significantly by Pedestrian connectivity

Intersection Density Scoring
Intersection Density Score Without SUPs
Poor Fair Excellent Average Density Score: Poor 68

Intersection Density Scoring
Intersection Density Score With SUPs
Fair Average Density Score: Good 142 Poor Excellent

Link-Node Scoring
Node-Link Score Without SUPs
Link-Node Ratio: 1.66

Link-Node Scoring
Node-Link Score With SUPs
Link-Node Ratio: 1.67

Seattle’s Mt. Baker Link LRT Station Example
RDI Measure: Pedestrian Access to LRT Station

Establish GIS Database
Study area
Light rail line
Street centerline
Parcel data

Create Pedestrian Network
Create Pedestrian Network
Illustrate Importance of “Hanford Steps”

Calculate Base Year RDI
Study Parcels (2,000 foot radius buffer from LRT station)
Pedestrian RDI to Mt. Baker Station
Baseline Conditions (assumes no Hanford Steps)
RDI Average = 0.67
Parcel RDI Desktop TM Metric Station Average RDI Score: Fair .67 Poor Good

Calculate PMP RDI
RDI Impact of Hanford Steps
Poor Good Parcel RDI Desktop TM Metric Station Average RDI Score: Good .72

Estimate RDI Enhancement
Difference between Baseline RDI and Hanford Steps RDI
Baseline: 58% of parcels above RDI 0.65 threshold.
Steps RDI: 73% of parcels above threshold.
Additional 40 more parcels.
RDI scoring can be used to sharpen plan priorities, particularly as federal and state funding becomes more competitive

Without link
Average: 296 intersections per mi 2
Poor Good Average Density Score: Fair 296

With project
Average: 302 intersections per mi 2
Marginal increase
Average Density Score: Fair 302 Poor Good

Seattle’s Beacon Hill Link LRT Station Example
RDI Measure: Bike Access to LRT Station

Import GIS Database
Study area
Light rail line
Street centerline
Parcel data

Create Bicycle Network
Create bike network
Bicycle Master Plan – existing conditions (2004)

Route Choice Analyses
Route Directness Index
Weighted Distance based on bicycle network characteristics

Calculate Base Year RDI
Study parcels (one-mile link distance)
Routes from parcels to Beacon Hill Station
Existing Conditions (2004)
Poor Good

Calculate BMP RDI
Added Bike Lanes noted in Bicycle Master Plan (BMP)
Poor Good

Estimate RDI Enhancement
Difference between Existing RDI and BMP RDI

Alternatives Analysis
Testing new Bicycle Boulevard project to improve E-W connectivity
Poor Good BMP oriented mostly north-south (arterials)… … instead of to LRT sta. RDI scoring can be used to identify supplemental master plans, using detailed route-choice analyses that integrate walkability and bicycle compatibility indices

RDI Comparison
Difference between BMP RDI and RDI with added Bike Boulevard project

Connectivity to LRT Baseline Measure: Bicycle Master Plan Plan Refinement: New Bicycle Boulevard Bicycle System Connectivity Scores Project Impact: Improved Connectivity Poor Good Poor Good

Non-motorized System Plan Evaluation
RDI Measure: Pedestrian Network Connectivity

Existing Conditions Shared-Use Path Connections Average RDI Score: Poor / Fair .58

New Shared-Use Paths Shared-Use Path Connections Average RDI Score: Fair / Good .66 14 % improvement

RDI – “Before & After” Shared-Use Path Connections Sensitive to Block Length Sensitive to Cul-de-Sac Length 305 ft 330ft RDI scoring is sensitive to urban design principles – because it directly measures connectivity

RDI – “Before & After” Delta Shared-Use Path Connections

Link-Node: Before Link-Node Ratio: 1.45 Nodes 74 Links 107 Ratio 1.45 Shared-Use Path Connections

Link-Node: After Shared-Use Path Connections Link-Node Ratio: 1.53 5.5 % improvement Nodes 92 Links 141 Ratio 1.53

Lakewood Sounder Commuter Rail Station Example
RDI Measure: Access to Commuter Rail Station

Lakewood’s NMTP New Pedestrian-Bicycle Connections RR Over-crossing I-5 Over-crossing

RDI - Baseline
Testing RDI: Land Use – to Sounder Station
Land Use (building structures) within One-Mile Radius
“ Baseline” = Existing Pedestrian System Connectivity
Poor Fair Good

RDI – After I-5 Crossing
Impact of I-5 Over-Crossing Improvements
Addition of Sidewalks and Bike Lanes
Poor Fair Good

RDI – After RR Crossing
Impact of New Railroad Over-Crossing
Exclusive Non-Motorized Facility
Poor Fair Good

Why Use Route Directness Index
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
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).
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

Route Choice Modeling
Non-motorized system quality, or levels and types of obstacles (impedances) are important factors to consider in walking and cycling route choice sub-models

How Can RDI Desktop TM Help?
Street Design Policy Implementation – measurable guidelines
Establish Non-motorized Neighborhood Connectivity Standards
Design guide thresholds for neighborhood planning site plan review – non-motorized concurrency
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
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

Contact
Andy Mortensen
WHAT TRANSPORTATION CAN BE
[email_address]
503.313.6946
www.transpogroup.com
Abu Dhabi | Kirkland | Seattle | Boise
* Trademarks provided under license from ESRI. *

CNU Summit 2009 RDI

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