Travel Demand Model (TDM)

Both the Measure C Growth Management Program and the State congestion management legislation require the Authority to develop and maintain a travel demand model. These models use 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 travel demand 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 the model to analyze the effects of its plans and programs, including the Countywide Comprehensive Transportation Plan and the Congestion Management Program.

The Authority's Decennial Model Update, completed in 2003, represents a major upgrade in modeling capabilities. The new model adds greater detail, in both the number of traffic analysis zones and the extent of the transportation network included, and is now integrated with geographic information systems, improving the geographical accuracy and display capabilities of the model.