Some reflections on the transition to activity-based models in the U.S.

It has now been nearly ten years since the first in a family of activity-based disaggregate microsimulation models of travel demand was applied in the US. Since that time, models in this same family have been applied in the cities of Portland, New York, San Francisco, Columbus, and Sacramento, and models are now under development for Denver, Oakland, Atlanta, Dallas,Lake Tahoe and other city and state government agencies. Although each ofthese model systems has its own distinguishing features, their similarities outweigh their differences, especially when contrasted to the traditional 4-step modelling approach. Now that there is evidence and experience from the application of a number of such models in the US, it is useful to consider whether or not the models appear to be living up to their promise.In cases where they are, examples are provided of what has been done withthe models that could not have been done with more conventional models. The first successful examples of activity-based model applications include various environmental impact studies, road-pricing projects and policies, large-scale rail / LRT/ BRT transit projects, and others. In cases where the models are less successful, the extent to which this is due to the models themselves or the way that they have been implemented and used is discussed. For the covering abstract see ITRD E137145.