Modeling

Travel Demand Modeling

Pierce County has developed and used travel demand models since the early 1990s. The model is used for many projects and programs applied by Pierce County and other agencies. Some model functions are mandated by state law, such as the Washington State Growth Management Act (GMA). The models also support decisions for construction of improved roadways and intersections, and alignment choices for new roadways. Read our guide to modeling to learn more.

Model Development

In 2009, the Transportation Planning and Programming Division began to refine and enhance our current travel demand model. Puget Sound Regional Council (PSRC) uses the regional travel demand forecasting model. Their model was a major guide for Pierce County's model.

The data that are being collected and processed include:

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)
local traits of Pierce County

How we use the models:

Road & Intersection Design

Projected traffic volumes are used to determine design features (e.g. number of lanes) for road and intersection projects.

Grant Applications

This model provides 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 parts of the Transportation Concurrency Annual Report.

Traffic Impact Fee (TIF) Program

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

Community Plans

Further modeling may be needed to support new or updated community plans, in the Pierce County Comprehensive Plan.

Environmental Studies

Traffic modeling is sometimes required for environmental studies of public and private projects. This ensures compliance with the State Environmental Policy Act (SEPA).

2015 Comprehensive Plan Update

A year 2030 land use and travel demand forecast was built as part of an update for a state mandate.

Corridor Studies

Future traffic volumes from the model are used to choose alignment alternatives for corridor studies.

Traffic Impact Analysis (TIA) Requirements

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

Interagency Coordination

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