Utility of Schedules: Theoretical Model of Departure-Time Choice and Activity-Time Allocation with Application to Individual Activity Schedules

The timing and duration of activities are important components of individual travel and activity behavior, affecting spatial interaction and mode choice decisions, highway and transit congestion, accessibility, and the general degree of social exclusion or inclusion experienced by the individual. The choices of timing and duration of activities are closely interrelated; however, few researchers have attempted to study this relationship. Instead strong separability assumptions have been made concerning the timing and duration dimensions. A utility theoretical model of joint activity-timing and duration choice is presented that addresses a number of the limitations of existing scheduling and time allocation models. How the theoretical model can be used to provide insight into the nature of the activity-scheduling process is outlined, and an algorithm is presented that can be used to operationalize the time allocation and activity-scheduling model. An estimable empirical form of the theoretical model is subsequently developed in which it is acknowledged that past and present activity and travel behavior decisions affect both existing and expected behavioral outcomes. How the model can be used to develop a number of disaggregate, activity-based accessibility measures is outlined, and with the aid of a simple hypothetical case study, a number of behavioral characteristics of the time-allocation and activity-scheduling model are demonstrated.