Abstract
This study explores how an individual might view the utility of alternate courses of action throughout the day. Its novel proposition is that utility for daily activity–travel alternatives is updated rather than accumulated. As the day progresses, the utility attached to various activities is updated for reasons of need, satiation, and various idiosyncratic associations with time, such as business hours, darkness, and cultural norms. Dynamic choice models are developed for individual activity–travel patterns and it is shown how time-dependent utility may be represented. The model system is being developed for the Portland, Oregon, region as part of a new activity-based travel demand forecasting system. Dynamic components of the model include time-dependent choices of activity episodes and their duration, locations, and travel modes. Results are presented of the next-activity-choice model component, which subsumes both activity frequency and duration in its specification.