During the 2017 National Regional Transportation Conference, Ian Varley provided case study examples from City Explained, LLC's work using scenario analysis.
3. Why Scenarios?
A scenario’s function:
- Van der Heijden (1996) - Scenarios
describe what the future could be
rather than what it will be.
- Schwartz (1996) - Scenarios are tools
that “aim to stretch thinking about
the future and widen the range of
alternatives considered”.
- The Battle of Dorking (1871)
4. Why Scenarios?
“We use scenario planning as a way to
address uncertainty in our future forecasts.
Money for transportation is tight. We look at
all our planned transportation infrastructure
improvements, and if they improve the
network in all scenarios, we feel much more
confident about making the investment.”
—Craig T. Casper, AICP
PPACG Regional Transportation Director
9. CommunityViz Software
What is it?
A decision support software that evaluates
competing future growth scenarios under
consideration by a community or region
(functioning as an extension of ArcGIS).
• Decision Support Apps
• Open Structure: Ties to ArcGIS,
Regional Travel Demand Models
(CUBE or TransCAD), Custom
Models
• Algorithmic Model & Geodesign
Enabled
• Various Spreadsheet Input / Output
Tools (Microsoft Excel)
• 3D Visualization Software
(Scenario 3D Analyst)
15. Scenario Family Tree
Algorithmic Models
• Deterministic or
microsimulation model
approach,
• Often complex, typically require
specialized staff
• Data intensive
Geodesign
• People driven, modeling takes a
secondary role as metrics
• Very scalable (as complicated as
you want them to be)
• Intentional: more directly linked
to a desired outcome
19. Bottom-Up Modeling
Development Status
Assignments
Land Suitability
Analysis
Calculations
Capacity &
Build-Out Estimates
Growth
Allocation
LSA measures the attractiveness
of individual parcels to
accommodate new development.
Physical features prevalent in the
study area were layered on a
parcel map, and calculations
performed to determine either
percent overlap or physical
proximity (as appropriate) for
each of the physical features in
relation to the individual parcels.
A numeric score between 0 – 100
was used to rank parcels in the
study area from least- to most-
suitable for development.
Growth allocation was performed
using build-out potential and land
suitability statistics calculated for
parcels in the study area.
Place types were used to describe
land use and urban form
characteristics in the study area.
Build-out potential estimates the
development yield for each parcel
based on it’s assigned
development status, place type, &
values assumed in the general
development lookup table.
Values generated for build-out
potential become the ‘supply’ for
allocating future year growth in
the study area.
The assignment of development
status to parcels in CommuntyViz
tells the model which set of
equations to use for estimating
development yield (build-out
potential), and whether new
growth is allowed in the parcel.
Constraints
Analysis
The area of a parcel identified
with one or more development
constraints (e.g., SWIM buffers,
recorded easements, etc.). These
areas are ‘off the table’ for
allocating new growth in
subsequent phases of the model.
22. Data Requirements
80% 20%
20% 80%
Readily Available Data Newly Created Data
Time Spent Collecting
Readily Available Data
Time Spent
Creating New Data
23. Communicating Scenario Processes
• Visuals
– Renderings
– Maps
– Infographics
– Online tools
• Concepts over numbers
“I’m a numbers guy and these aren’t my numbers”
24. Give It To Me Straight…
Do I need a consultant?
Sometimes.
Do I need a dedicated staff person or persons?
Usually.
Will I need to ask questions and do research?
Always.
Where do I start if I’m thinking about doing this?
Talk to people who have done it.
25. Keeping Scenario Processes Manageable
• Focus like a panther: identify your
objectives and pursue them
• Sometimes less is more
• Encourage regular communicating
with staff and stakeholders
• When communicating with the
public, make it as simple as you can,
then try and make it simpler
