Travel Demand Modeling

Pierce County has developed and used travel demand models since the early 1990s. The model is extensively used for numerous projects and programs implemented by Pierce County and other agencies. Some model applications are mandated by state law, particularly the Washington State Growth Management Act (GMA). Non-mandated applications are also completed to support internal and external decisions regarding construction of improved roadways and intersections and alignment choices for new roadways. Read our guide to modeling for more information.

Model Development

In 2009, the Transportation Planning and Programming Division embarked on a multi-year model development effort that will significantly refine and enhance our current travel demand model. One of the main goals of this effort is to attempt to achieve closer consistency with the regional travel demand forecasting model developed by the Puget Sound Regional Council (PSRC).

Among the datasets that are being collected, processed and analyzed are current and future land use data (population, housing, and employment), traffic counts, regional travel surveys, current and future multi-modal transportation networks (including bus, rail, and non-motorized modes) and the local characteristics of Pierce County.

How we use the models that have been developed:

Road & Intersection Design

The projected traffic volumes from the model are used to determine design features (e.g. number of lanes) for road and intersection projects.

Grant Applications

This model is used to provide traffic volumes and other travel statistics for grant applications for federal and state funding programs.

Transportation Concurrency

Existing and six-year arterial forecasts from the model are incorporated into the Transportation Concurrency Annual Report.

Traffic Impact Fee (TIF) Program

A substantial modeling effort was a key component in the development of the Traffic Impact Fee (TIF) Program. Any updates to the TIF program will likely require additional modeling efforts.

Community Plans

Additional future modeling may be needed to support any new or updated community plans, which are components of the Pierce County Comprehensive Plan.

Environmental Studies

Traffic modeling is sometimes required as part of the environmental studies for both public and private projects in order to comply with the State Environmental Policy Act (SEPA) requirements.

2011 Comprehensive Plan Update

A year 2030 land use and travel demand forecast is anticipated as part of this state-mandated update.

Corridor Studies

Future traffic volumes from the model are used for identifying and choosing alignment alternatives for corridor studies.

Traffic Impact Analysis (TIA) Requirements

Traffic modeling is sometimes necessary for the Traffic Impact Analysis required for major development proposals.

Interagency Coordination

Cities and other agencies routinely request modeling assistance and other data, through interagency coordination, for use in their transportation studies.
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