Companionship and time investment in social fields at different life cycle stages: Implications for activity and travel modeling and simulation

In this paper, we employ structural regression models to identify the differences and commonalities among life cycle stages in daily interpersonal contacts and their activity-travel time allocation. The daily contacts (with family, friends, schoolmates, co-workers, clubmates, and others), duration of activities by type, and travel time are the endogenous variables of the system. Life-cycle stages, day of the week, and accessibility are the exogenous variables. The model finds life-cycle dependent roles in interpersonal interactions and intra-household contacts and friends are significant in explaining service, shopping, home-leisure, and out of home social activity durations. Moreover, the many significant indirect paths of this model show we should include human interactions and paths of influence in activity models. We also compare the direct and indirect influence between two models, one that includes number of daily contacts and a second model without daily contacts. Three groups are found as the most sensitive in allocation of time when controlling for daily contacts and they are children younger than 17 years, persons in home duties, and college students. In addition, allocation of time to discretionary activities is the most sensitive to specifications that control for number of daily contacts.