The state of activity-based modeling practice in the United States

This special issue calls for “new foundational concepts and methods for predicting, and a close coupling of, travel behavior related to passenger and commodity movements.” This call assumes that the current foundational concepts and methods are insufficient for the task at hand, specifically simulating traveler behavior in a post-COVID world. But what, exactly, are the current foundational concepts and methods? This paper fills a gap in the literature and sets the stage for the special issue by documenting the current state of passenger travel modeling practice. A 2007 article published in this journal described what was then the current state of the practice and suggested future directions for what was then the relatively new “activity-based” modeling paradigm (Davidson et al., 2007). These models have now reached maturity in the United States. One outcome of this maturity is that model developers and model owners are less likely to publish their methods in academic journals than during the earlier years of activity-based model development. Researchers must therefore seek out agency model documentation to understand the state of travel modeling practice, which is rarely done. We seek to address this information gap by documenting the current state of the practice in activity-based travel modeling, with references to relevant practical modeling systems, and reflect on the evolution of practical models since their initial deployments. These references can be used by academics as “baselines” to demonstrate the comparative value of new foundational concepts and methods. We also identify and discuss obstacles to widespread adoption of activity-based models and suggest research threads that would add value to travel modeling practice.