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

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

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

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

Example Specifications AMPO Travel Modeling Work Group Meeting

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