Travel Demand Model

Both the Measure C Growth Management Program and the State congestion management legislation require the Authority to develop and maintain a Countywide computerized travel demand forecasting model. The Countywide Model uses information on current and future population and employment, transit ridership, expected roadway improvements, and observed travel behavior to forecast traffic on the regional transportation system. The Countywide Model is used in several ways:

  • Local agencies use it to analyze the effects of new development and changes in their general plans.
  • Various agencies, including the Authority and Caltrans, use it to analyze the effects on new transportation improvements.
  • The Authority uses it to analyze the effects of its plans and programs, including the Countywide Comprehensive Transportation Plan and the Congestion Management Program.
  • Every ten years the Authority updated the Countywide Model through the Decennial Model Update. Each update adds greater detail, in both the number of traffic analysis zones and the extent of the transportation network included. Currently, the model is being updated to transition from a “trip-based” model to an “activity-based” model. Also, the model is being used to explore the use of smart phones for ridesharing (including Lyft and Uber) and ultimately fully autonomous cars. 




  • Decennial Model Update-Executive Summary
  • Decennial Model Update-CCTA Travel Model Documentation
  • Decennial Model Update- CCTA Model User's Guide
  • Decennial Model Update
  • KML file