Abstract Household members interact in many ways during their daily activity-and travel-related decisionmaking. Consequently, the activity-travel patterns of all household members become interdependent. There has been an increasing realization that such household interdependencies have to be accommodated explicitly within activity-based models for accurate forecasts of travel patterns and for the realistic evaluation of the impacts of policy actions. As a result, during the last few years, there have been a significant number of studies aimed to modeling the household interactions. However, critical gaps exist in some key areas. For example, regarding joint participation on activities, many gaps still exist in understanding the activity eng...