Activity-Based Models

This article provides an overview of activity-based models (ABMs), their relative merits over traditional four-step trip-based models, and different design approaches to modeling disaggregate activity-travel choices. Specifically, the handling of time-space constraints and intra and inter-person dependency among trips made by household members within ABMs are discussed. Next, the article describes two key components of most ABMs including (1) the activity generation component which predicts the activity participation choices of all household members, and (2) the activity scheduling component that packages activities into tours as well as determines additional attributes for each activity including the travel mode, departure time, duration, and location. Also, a brief overview the random utility maximization framework that is commonly used to predict the activity and travel choices was discussed. Also, the survey data needs for training the choice models within ABMs and supplementary modeling systems that provide input to ABMs including the synthetic population generator that creates synthetic, another ancillary module that predicts medium-long term household and person choices that influence day-to-day activity travel choices, the traffic assignment module that provides travel times and costs, and land-use models that provide regional residential and business location patterns are briefly discussed. In addition, the article discusses recent trends in the move towards development of integrated modeling systems that capture supply and demand interactions at both shorter (with dynamic traffic assignment) and longer time (with land-use models) scales.