1. Incorporating Uncertainty Analysis into Forecasting
Group Discussion
AMPO Travel Modeling Work Group
Chicago, Illinois
October 1, 2009 1

2. AMPO Travel Modeling Work Group Meeting
Why Bother?
A new way of thinking about forecasting
Insights, not just model mechanics
Range of possible outcomes
Another approach for quality control checks
Information for decision makers
Upper/lower bound, most likely
Honesty in presentation of forecasts
Predicted-versus-actual outcomes
AMPO Travel Modeling Work Group Meeting 2

3. Example: Forecast Build-up
Series of forecasts for:
Today
Plus future transit network
Plus new transit behaviors
Plus future trip tables
Plus future highway congestion
Plus future parking costs
Plus alternative land use (?)
Choice riders
Park/ride etc.
Guideway effects
AMPO Travel Modeling Work Group Meeting

4. Example: Honolulu Rail Study
Rail-trip Build-up
Forecast
Attribute #1 #2 #3 #4 #5 #6 #7 #8
Person trips --
’05
’18
‘30
’30
Highway speeds
‘05
’30-
Bus speeds
’05+
Transit network
Transit demand
’05a
’05p
’18p
’30h
’30b
’30c
Rail trips per day
60k
73k
77k
86k
72k
118k
87k
Notes:
- Transit demand ’05a is the 2005 on-board survey.
- Bus speeds ’05+ are based on highway speeds from the assignment of 2005 person trips onto the 2030 highway network.
- Highway speeds ’30- are from the assignment of 2030 person trips onto the 2005 highway network.
AMPO Travel Modeling Work Group Meeting

5. Example Specifications
AMPO Travel Modeling Work Group Meeting

6. AMPO Travel Modeling Work Group Meeting
Discussion Points
Model documentation
Assessment of model plausibility
What it does/does not know well
Markets, modes, behaviors
Results of forecast tests
Consistency with similar projects
Key drivers of the forecasts
Demographic/network inputs
Alternative assumptions
AMPO Travel Modeling Work Group Meeting 6