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Figure 2-2 Simplified outline of transportation modeling process, showing connections to American Community Survey products

SOURCE: Adapted from workshop presentation by Beth Jarosz.

These underlying demographic and economic forecasts of the basic composition of the population are further scrutinized in what Jarosz described as subregional or “neighborhood”-level forecasts—drilling into finer geographic detail than the region as a whole, and attempting to predict how the population and characteristics will be distributed spatially over time.

The next step is application of a synthetic population model—the basic idea of which is to simulate actions by all actors in the transportation network and model how they will travel through the system. This work is done in tandem with a separate activity-based transportation model (also shown in Figure 2-2) that makes forecasts to simulate individual trips within the system (e.g., when commuters leave for work in the morning, whether they make stops en route to work or home, and when they arrive at work or home).12 For the synthetic pop-

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12In the case study/agenda book for the workshop, Guy Rousseau describes the synthetic pop-



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