Model Inputs and Outputs

In the broadest sense, the TPB's transportation models consist of three elements:

1. Input data,
2. Models (mathematical procedures and representations), and
3. Results ("output").

Model Inputs

The two basic inputs to TPB's models are:

• Forecasts of future population, households, and employment throughout the region; and
• Information about future transportation networks -- changes that are planned, or potential changes to be tested -- that would improve today's transportation system.

Population and employment estimates are developed through COG’s Cooperative Forecasting Program, which is conducted every few years and reflects the best judgments of local officials regarding the location of future housing, commercial and industrial development within the region.  The Cooperative Forecasting Program is overseen by the Cooperative Forecasting and Data Subcommittee (CFDS), a technical subcommittee to the Planning Directors Technical Advisory Committee (PDTAC) and the Metropolitan Development Policy Committee (MDPC).

Model Outputs

• Vehicular volumes on roads (flows on links)
• Speeds on links
• Origin/destination patterns - These are represented by zone-to-zone trip tables, which are usually segmented by travel mode.
• Mode splits
• Emissions from cars and trucks (requires post processor and emissions models)