ILUTE Social Networks and Activity-travel modelling: some research ideas Juan Antonio Carrasco University of Toronto Student Caucus Workshop Toronto, September 13, 2003

ILUTE The importance of networks

ILUTE Outline What is a social network? Why social networks? Potential ideas Potential methodologies Conclusion

ILUTE What is a social network? Study of social structure and its effects Social structure = social network

ILUTE What is a social network? Nodes (actors)

ILUTE What is a social network? Relationships (ties)

ILUTE Why social networks? Social network models

ILUTE Why social networks? Activity-travel behaviour models Are we doing a good job?

ILUTE Why social networks? Axhausen (2002): –“Need to underpin our travel models with a better understanding of the social structures of daily life and, as we implicitly forecast/speculate about them when we predict travel behaviour over long time horizons, anyway…” New perspective  incorporation of social space Relationship between social and physical space Ties: “links” that indirectly represent potential activity and travel between the actors Need to explicitly incorporate interactions

ILUTE Potential ideas De-emphasis on psychological and economic explanations –Focus on relationships –Behaviour from a different perspective: Contrasts with psychologistic explanations that treat individuals as independent units-of-analysis Social network data sets often include information about attributes, such as age, gender, ethnicity, and beliefs. However, network analysis does not treat social systems as the sum of individual attributes, but links attribute data with relational and structural data”

ILUTE Potential ideas Representation of constraints and travel behaviour –“Behaviour is interpreted in terms of structural constraints on activity, rather than in terms of voluntaristic inner forces” (Wellman and Berkowitz, 1988) –Structural theory allow relationships to be asymmetrical –Link with Hägerstrand's (1970) ideas Coupling  interactions Capability  physical – social space Authority  asymmetry

ILUTE Potential ideas Changes in the way people interact (Wellman, 2001) –Person-to-person  door-to-door  person-to-person –Information and communication technology (ICT) Specialization of networks –“Achieved” (e.g. lifestyle) versus “ascriptive” (e.g. income) characteristics –Role-to-role relationships  New ways to segment activities and travel

ILUTE Potential methodologies Variety of descriptive and analytical tools: –Centrality and prestige –Locational properties –Structural equivalence, position and roles –Dyadic and triadic methods

ILUTE Potential methodologies Statistical formation of ties and network formation –Simulation and statistical techniques (e.g. kinship) –Stochastic simulation models  “sociomatrix” as random variables: Distributions Random components –Log-probabilistic models – Autocorrelation over the social space (similar to spatial econometrics) –Representation of personal and “linked” lives

ILUTE Conclusions Need to incorporate interactions among individuals Potential for applying concepts and theories Potential for applying methodology The challenge…

ILUTE Social Networks and Activity-travel modelling: some research ideas Juan Antonio Carrasco University of Toronto Student Caucus Workshop Toronto, September 13, 2003