Coevolving social and transportation networks

Abstract

A component of work and non-work travel may be plausibly explained by the need for individuals to be co-present in order socially interact. Successful socializing requires maintaining and exploiting relationships, fulfilling obligations, and perhaps optimization of contacts. A social network is a way to map relationships and to quantify conduits of information, services, opportunity, and power. People must be able to navigate both their relationships and physical space in order to find other people and facilities which can provide the services they need. The result is that travel behavior and social structures affect each other. This research examines hypotheses of the interactions between social networks and trip generation. Models of social networks should be used by planners if their effects are significant and distinguishable from factors currently incorporated into transportation models. A multi-agent-based network evolution model is presented in which social visits are generated by a set of attraction parameters which include agent attributes, travel impedance, and descriptors of the actors’ position in the social network topology. The trips are constrained by the agent’s travel budget, and dynamic equilibrium is maintained by removing or weakening old links. The destination choice is thus a tradeoff between cost and the need for co-presence, marked by correlations between actors in the changing social network. The interactions are monitored using a statistical toolbox from social network analysis and placed in the context of findings from network science literature on network evolution, as well as from empirical work in sociology on real social networks. The behavior model used for social networking is described, and results from an ensemble run are presented. A sample case of a transportation “improvement” is also presented, to illustrate the way in which the social network adapts to changes in transportation costs that ease spatial searches.