Modeling and Forecasting

With state-of-the-practice computer simulation tools, the Travel Demand Modeling Group prepares traffic forecasts for local, regional and statewide planning and design studies. The modeling group also provides technical guidance, training and assistance to MPOs, cities, counties, other government agencies and their consultants.  The Arizona Statewide Travel Demand Model (AZTDM) simulates the interaction between people and the transportation system. The Travel Demand Modeling Group uses a series of mathematical models that simulate human travel behavior to prepare the travel forecasts used for road design and transportation planning. Travel forecasts are produced for planning horizons up to 30 years in the future based on population and employment growth projections established by the Arizona State Demographer's Office.

Travel Model Development

The Arizona Statewide Travel Demand Model (AZTDM) was first developed in 2008 for use in ADOT's Statewide Transportation Framework Study. This first-generation statewide planning tool provided the building blocks for the next more detailed second-generation model. The AZTDM2 model incorporated the traffic analysis zone geography and road network used in the MPO models. Where the AZTDM1 had approximately 1,000 zones, AZTDM2 had more than 6,000 zones. Other enhancements for the AZTDM2 included a destination choice trip distribution model, a short-distance truck model, a long-distance personal travel model and a long-distance truck model.

ADOT is completing development of its third-generation statewide model (AZTDM3). Where AZTDM1 and AZTDM2 were highway-only models, the AZTDM3 adds a public transit mode choice component. AZTDM3 also includes enhancements to other model components such as auto availability.

Travel Model Application

Since its first application in the Statewide Transportation Framework Study, the AZTDM has supported numerous ADOT planning efforts. These include the Interstate 11 and Intermountain West Corridor Study, the North-South Corridor Study in Pinal County, the Arizona Key Commerce Corridors study and ADOT's Planning-to-Programming process.