Overview

PierceCast is an activity-based model system, derived from SoundCast, that represents the travel behavior of each individual and household throughout the Pierce County along with King, Kitsap, and Snohomish counties. The model depicts travel behaviors that depend on the built environment and demand from other users. PierceCast outputs transportation network measures such as highway volumes in one-hour periods in a future year, or number of boardings on a transit line. It also outputs measures related to people like average distance to work by home county or the number of transit trips different types of people will take.

The three main components of PierceCast are:

• person trip demand in the DaySim activity-based model
• submodels including external, truck, and special trips (to unique locations like airports and military bases)
• trip assignment onto road networks
• output preparation for analysis

DaySim is a modeling approach and software platform to simulate resident daily travel and activities on a typical weekday for the residents of a metropolitan region or state. In essence, DaySim replaces the trip generation, trip distribution and mode choice steps of a 4-step model, while representing more aspects of travel behavior (auto ownership, trip chaining, time of day scheduling, detailed market segmentation, etc.) Daysim integrates with EMME by generating resident trip matrices for assignment and uses the network skims from assignment for the next global iteration of DaySim.

[The major inputs to PierceCast are transportation networks and modeled household and employment data from UrbanSim. In Daysim, The Population Synthesizer (PopSyn) creates a synthetic population, comprised of Census PUMS households, that is consistent with regional residential, employment and school enrollment forecasts. Long-term choices (work location, school location and auto ownership) are simulated for all members of the population. The Person Day Activity and Travel Simulator (DaySim) creates a one-day activity and travel schedule for each person in the population, including a list of their tours and the trips on each tour.] [Need Update]

The trips predicted by DaySim are aggregated into EMME trip matrices and combined with predicted trips for special generators, external trips and commercial traffic into time- and mode-specific trip matrices. The EMME network traffic assignment models load the trips onto the network. Traffic assignment is iteratively equilibrated with the Long Term Choice Simulator, DaySim and the other demand models. [The parcel level land use inputs come from UrbanSim.] [Need Update]

Basic Model Flow

A simplified description of model processes is shown below. Initial setup scripts are run only once, while iterative steps are repeated until a global convergence is met.

Initial Setup

• Create empty banks by time of day
• Create Emme project folders
• Copy scenario inputs to local directory (inputs -> scenario)
• Accessibility calculations
• Import networks for all time periods

Iterative Model Steps

• Assignment and skim creation (using free flow demand first)
• Daysim demand models
• Truck model
• Supplemental trips (externals, airport)
• Check for global convergence

Final Model Steps

• Generate summaries

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Next: DaySim Person Trip Demand Models