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
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
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
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
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
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
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.