Transportation Research Part A: Policy and Practice, 2009
This paper presents a social activity-travel generation model, which explicitly incorporates the ... more This paper presents a social activity-travel generation model, which explicitly incorporates the individual's social dimension through the concept of personal networks, modeling the multilevel structure of social relations defined by these networks. The objective of the analysis is to study the relevance of the social dimension as a source of explanation of social activity-travel generation behavior between an individual and each relevant person of their social life. The paper uses a disaggregated perspective of personal networks, explicitly incorporating the characteristics of each network member as well as the characteristics of the overall social structure. Using an ordinal multilevel specification that accounts for the social network in which individuals are embedded, four dimensions are studied: personal characteristics, "with whom" activities are performed, social network composition and structure, and ICT (information and communication technology) interaction. The results show that a proper and complete understanding of social activity generation requires going beyond the individualistic paradigm, explicitly incorporating the role of the social dimension in the study of this decision making process.
Our study is part of the broad debate about the role of distance and technology for interpersonal... more Our study is part of the broad debate about the role of distance and technology for interpersonal contact. To the best of our knowledge, this is the first study that systematically and explicitly compares the role of distance in social networks pre-and post-Internet. We analyze the effect of distance on the frequency of email, phone, face-to-face and overall contact in personal networks, and we compare the findings with its pre-Internet counterpart whose data were collected in 1978 in the same East York, Toronto locality. We use multilevel models with spline specification to examine the nonlinear effects of distance on the frequency of contact. We compare these effects for both very close and somewhat close ties, and for different role relationships: immediate kin, extended kin, friends and neighbours. The results show that email contact is generally insensitive to distance, but tends to increase for transoceanic relationships greater than 3,000 miles apart.
This paper presents a new tour-based mode choice model. The model is agent-based: both households... more This paper presents a new tour-based mode choice model. The model is agent-based: both households and individuals are modelled within an object-oriented, microsimulation framework. The model is household-based in that inter-personal household constraints on vehicle usage are modelled, and the auto passenger mode is modelled as a joint decision between the driver and the passenger(s) to ride-share. Decisions are modelled using a random utility framework. Utility signals are used to communicate preferences among the agents and to make trade-offs among competing demands. Each person is assumed to choose the "best" combination of modes available to execute each tour, subject to auto availability constraints that are determined at the household level. The household's allocations of resources (i.e., cars to drivers and drivers to ride-sharing passengers) are based on maximizing overall household utility, subject to current household resource levels. The model is activity-based: it is designed to be integrated within a household-based activity scheduling microsimulator. The model is both chainbased and trip-based. It is trip-based in that the ultimate output of the model is a chosen, feasible travel mode for each trip in the simulation. These trip modes are, however, determined through a chain-based analysis. A key organizing principle in the model is that if a car is to be used on a tour, then it must be used for the entire chain, since the car must be returned home at the end of the tour. No such constraint, however, exists with respect to other modes such as walk and transit. The paper presents the full conceptual model and an initial empirical prototype.
Abstract Conceptual and empirical models of the propensity to perform social activity–travel beha... more Abstract Conceptual and empirical models of the propensity to perform social activity–travel behavior are described, which incorporate the influence of individuals' social context, namely their social networks. More explicitly, the conceptual model develops the concepts of egocentric social networks, social activities, and social episodes, and defines the three sets of aspects that influence the propensity to perform social activities: individuals' personal attributes, social network composition, and information and communication technology ...
Transportation Research Record: Journal of the Transportation Research Board, 2008
Hägerstrand's seminal argument that regional science is about people and not only locations is st... more Hägerstrand's seminal argument that regional science is about people and not only locations is still a compelling and challenging idea when studying the spatial distribution of activities. In the context of social activity-travel behavior (hosting and visiting), this issue is particularly fundamental since the individual's main motivation to perform social trips is mostly with whom they interact rather than where they go. A useful approach to incorporate the travelers' social context is by explicitly studying the spatial distribution of their social networks, focusing on social locations as emerging from their contacts, rather than analyzing social activity locations in isolation. In this context, this paper studies the spatial distribution of social activities, focusing on the home distances between specific individuals (egos) and their network members (alters) with whom they socialize --serving as a proxy to study social activity-travel location.
Transportation Research Record: Journal of the Transportation Research Board, 2008
Activity-based approaches to travel demand modeling are increasingly moving from theoretical to o... more Activity-based approaches to travel demand modeling are increasingly moving from theoretical to operational models. In this context, agent-based micro-simulation models are a promising approach since they explicitly conceive travel as an emergent phenomenon from peoples' activity characteristics, and more explicitly, from their activity scheduling processes. Behaviorally, activity-scheduling processes are influenced not only by individuals' characteristics, but also by the other people with whom they interact. Thus, the activity scheduling process has an intrinsic social context. Using social activities as a case study, the objective of this paper is to empirically investigate the relationship between the social context (measured by with whom the respondents interacted) and two key aspects of activity scheduling: start time and duration. Econometric models of the combined decisions regarding "with whom" to participate and when to start or how much time to spend on are estimated to investigate the correlations between "with whom" and the start time / duration decisions. Data collected by a seven-day activity diary survey are used for the model developments. Findings suggest that the social context has a relevant role in activity scheduling processes. For example, the investigations indicate that it is "with whom" we socialize what influences the social activity scheduling processes more than the travel time or the distances to social travel. Overall, and additionally to the theoretical understanding of the questions posed to investigate in this paper, the models serve as an empirical support for agent-based microsimulation models that could incorporate the role of social networks in activity scheduling attributes.
Transportation Research Part B: Methodological, 2009
An integrated model of vehicle transactions, activity scheduling and mode choice is estimated bas... more An integrated model of vehicle transactions, activity scheduling and mode choice is estimated based on a retrospective vehicle transaction survey in the Toronto Area. First a conceptual framework is presented which links long run decisions of automobile transactions with short run decisions of activity participation, travel and mode choice. The concept of activity/travel stress is introduced to represent the difference between household activity/travel with the current vehicle fleet and that associated with alternative fleets due to ...
Transportation Research Part A: Policy and Practice, 2011
Abstract: This article presents the papers published in this issue of Transportation Research Par... more Abstract: This article presents the papers published in this issue of Transportation Research Part A. The papers were presented at the international workshop" Frontiers in Transportation II: Social Interactions," held October 13-16, 2007 in Amsterdam, Netherlands. The workshop was organized around eight topics: simulation studies, challenges of large scale systems, econometric approaches, innovative data collection, social context, qualitative methods, aggregate influences, and the role of information in planning practice. The papers in this ...
The popular hierarchical or nested logit model that has been the recent source of heated discussi... more The popular hierarchical or nested logit model that has been the recent source of heated discussions in the literature is reviewed and critically examined. The fundamental underpinnings of the model are first presented in a concise and easy-to-understand fashion and then used to assess each controversy in turn. Monte Carlo simulation is also used to examine some problems that are not possible to address by just resorting to the theory. The main conclusion is that all the model hypotheses are both essential and unambiguous ...
Tijdschrift voor economische en sociale geografie, 2008
This paper explores the relationship between travel behaviour, ICT use and social networks. Speci... more This paper explores the relationship between travel behaviour, ICT use and social networks. Specifically, we outline a theory of social action that can inform how ICTs relates to social activity travel and explore the efficacy of this theory in an empirical setting. We begin by outlining two factors that influence the propensity to travel: an individual's will to initiate events with members of one's social network, referred to as agency , and the social accessibility of network members themselves. Social accessibility defines a series of practical constraints for social-activity travel and agency defines the extent to which an individual will actively work within these constraints to maintain their social network. The theoretical section first unpacks these concepts while embedding them in the research literature, finishing with an operationalisation of agency and social accessibility. Using this theory, the empirical section investigates the relationship between agency, social accessibility, and factors associated with both the respondents and their personal networks. More specifically, we examine how agency levels of interaction are related to differences in demographics, global measures of network structure and composition, and measures of media use, particularly of Internet and telephone. We conclude that individuals who are proximate or more active are more likely to maintain reciprocal relationships, and that more distant or infrequent ties require greater maintenance on the individual's part. We believe that studies of activity-travel and ICTs will benefit from a theoretical lens that articulates some of the transformative effects of ICTs on travel vis-à-vis its effects on social life. Social accessibility and agency can help focus that lens thereby enabling researchers to make potentially more elaborate and realistic models that move beyond the spatial and temporal dimensions into social dimensions.
We describe an interview-based data-collection procedure for social network analysis designed to ... more We describe an interview-based data-collection procedure for social network analysis designed to aid gathering information about the people known by a respondent and reduce problems with data integrity and respondent burden. This procedure, a participant-aided network diagram (sociogram), is an extension of traditional name generators. Although such a diagram can be produced through computer-assisted programs for interviewing (CAPIs) and low technology (i.e., paper), we demonstrate both practical and methodological reasons for keeping high technology in the lab and low technology in the field. We provide some general heuristics that can reduce the time needed to complete a name generator. We present findings from our Connected Lives field study to illustrate this procedure and compare to an alternative method for gathering network data.
Abstract: A conceptual model of social activity-travel behaviour is described, incorporating an a... more Abstract: A conceptual model of social activity-travel behaviour is described, incorporating an activity-scheduling framework which explicitly includes the influence of the individual's social context. More explicitly, the model develops the concepts of social networks, activities, and social episodes, and defines the individual's social activity generation and spatial distribution in a context of his/her social networks. Also, empirical findings regarding the influence of social network characteristics on individual's socialising patterns are ...
Transportation Research Part A: Policy and Practice, 2009
This paper presents a social activity-travel generation model, which explicitly incorporates the ... more This paper presents a social activity-travel generation model, which explicitly incorporates the individual's social dimension through the concept of personal networks, modeling the multilevel structure of social relations defined by these networks. The objective of the analysis is to study the relevance of the social dimension as a source of explanation of social activity-travel generation behavior between an individual and each relevant person of their social life. The paper uses a disaggregated perspective of personal networks, explicitly incorporating the characteristics of each network member as well as the characteristics of the overall social structure. Using an ordinal multilevel specification that accounts for the social network in which individuals are embedded, four dimensions are studied: personal characteristics, "with whom" activities are performed, social network composition and structure, and ICT (information and communication technology) interaction. The results show that a proper and complete understanding of social activity generation requires going beyond the individualistic paradigm, explicitly incorporating the role of the social dimension in the study of this decision making process.
Our study is part of the broad debate about the role of distance and technology for interpersonal... more Our study is part of the broad debate about the role of distance and technology for interpersonal contact. To the best of our knowledge, this is the first study that systematically and explicitly compares the role of distance in social networks pre-and post-Internet. We analyze the effect of distance on the frequency of email, phone, face-to-face and overall contact in personal networks, and we compare the findings with its pre-Internet counterpart whose data were collected in 1978 in the same East York, Toronto locality. We use multilevel models with spline specification to examine the nonlinear effects of distance on the frequency of contact. We compare these effects for both very close and somewhat close ties, and for different role relationships: immediate kin, extended kin, friends and neighbours. The results show that email contact is generally insensitive to distance, but tends to increase for transoceanic relationships greater than 3,000 miles apart.
This paper presents a new tour-based mode choice model. The model is agent-based: both households... more This paper presents a new tour-based mode choice model. The model is agent-based: both households and individuals are modelled within an object-oriented, microsimulation framework. The model is household-based in that inter-personal household constraints on vehicle usage are modelled, and the auto passenger mode is modelled as a joint decision between the driver and the passenger(s) to ride-share. Decisions are modelled using a random utility framework. Utility signals are used to communicate preferences among the agents and to make trade-offs among competing demands. Each person is assumed to choose the "best" combination of modes available to execute each tour, subject to auto availability constraints that are determined at the household level. The household's allocations of resources (i.e., cars to drivers and drivers to ride-sharing passengers) are based on maximizing overall household utility, subject to current household resource levels. The model is activity-based: it is designed to be integrated within a household-based activity scheduling microsimulator. The model is both chainbased and trip-based. It is trip-based in that the ultimate output of the model is a chosen, feasible travel mode for each trip in the simulation. These trip modes are, however, determined through a chain-based analysis. A key organizing principle in the model is that if a car is to be used on a tour, then it must be used for the entire chain, since the car must be returned home at the end of the tour. No such constraint, however, exists with respect to other modes such as walk and transit. The paper presents the full conceptual model and an initial empirical prototype.
Abstract Conceptual and empirical models of the propensity to perform social activity–travel beha... more Abstract Conceptual and empirical models of the propensity to perform social activity–travel behavior are described, which incorporate the influence of individuals' social context, namely their social networks. More explicitly, the conceptual model develops the concepts of egocentric social networks, social activities, and social episodes, and defines the three sets of aspects that influence the propensity to perform social activities: individuals' personal attributes, social network composition, and information and communication technology ...
Transportation Research Record: Journal of the Transportation Research Board, 2008
Hägerstrand's seminal argument that regional science is about people and not only locations is st... more Hägerstrand's seminal argument that regional science is about people and not only locations is still a compelling and challenging idea when studying the spatial distribution of activities. In the context of social activity-travel behavior (hosting and visiting), this issue is particularly fundamental since the individual's main motivation to perform social trips is mostly with whom they interact rather than where they go. A useful approach to incorporate the travelers' social context is by explicitly studying the spatial distribution of their social networks, focusing on social locations as emerging from their contacts, rather than analyzing social activity locations in isolation. In this context, this paper studies the spatial distribution of social activities, focusing on the home distances between specific individuals (egos) and their network members (alters) with whom they socialize --serving as a proxy to study social activity-travel location.
Transportation Research Record: Journal of the Transportation Research Board, 2008
Activity-based approaches to travel demand modeling are increasingly moving from theoretical to o... more Activity-based approaches to travel demand modeling are increasingly moving from theoretical to operational models. In this context, agent-based micro-simulation models are a promising approach since they explicitly conceive travel as an emergent phenomenon from peoples' activity characteristics, and more explicitly, from their activity scheduling processes. Behaviorally, activity-scheduling processes are influenced not only by individuals' characteristics, but also by the other people with whom they interact. Thus, the activity scheduling process has an intrinsic social context. Using social activities as a case study, the objective of this paper is to empirically investigate the relationship between the social context (measured by with whom the respondents interacted) and two key aspects of activity scheduling: start time and duration. Econometric models of the combined decisions regarding "with whom" to participate and when to start or how much time to spend on are estimated to investigate the correlations between "with whom" and the start time / duration decisions. Data collected by a seven-day activity diary survey are used for the model developments. Findings suggest that the social context has a relevant role in activity scheduling processes. For example, the investigations indicate that it is "with whom" we socialize what influences the social activity scheduling processes more than the travel time or the distances to social travel. Overall, and additionally to the theoretical understanding of the questions posed to investigate in this paper, the models serve as an empirical support for agent-based microsimulation models that could incorporate the role of social networks in activity scheduling attributes.
Transportation Research Part B: Methodological, 2009
An integrated model of vehicle transactions, activity scheduling and mode choice is estimated bas... more An integrated model of vehicle transactions, activity scheduling and mode choice is estimated based on a retrospective vehicle transaction survey in the Toronto Area. First a conceptual framework is presented which links long run decisions of automobile transactions with short run decisions of activity participation, travel and mode choice. The concept of activity/travel stress is introduced to represent the difference between household activity/travel with the current vehicle fleet and that associated with alternative fleets due to ...
Transportation Research Part A: Policy and Practice, 2011
Abstract: This article presents the papers published in this issue of Transportation Research Par... more Abstract: This article presents the papers published in this issue of Transportation Research Part A. The papers were presented at the international workshop" Frontiers in Transportation II: Social Interactions," held October 13-16, 2007 in Amsterdam, Netherlands. The workshop was organized around eight topics: simulation studies, challenges of large scale systems, econometric approaches, innovative data collection, social context, qualitative methods, aggregate influences, and the role of information in planning practice. The papers in this ...
The popular hierarchical or nested logit model that has been the recent source of heated discussi... more The popular hierarchical or nested logit model that has been the recent source of heated discussions in the literature is reviewed and critically examined. The fundamental underpinnings of the model are first presented in a concise and easy-to-understand fashion and then used to assess each controversy in turn. Monte Carlo simulation is also used to examine some problems that are not possible to address by just resorting to the theory. The main conclusion is that all the model hypotheses are both essential and unambiguous ...
Tijdschrift voor economische en sociale geografie, 2008
This paper explores the relationship between travel behaviour, ICT use and social networks. Speci... more This paper explores the relationship between travel behaviour, ICT use and social networks. Specifically, we outline a theory of social action that can inform how ICTs relates to social activity travel and explore the efficacy of this theory in an empirical setting. We begin by outlining two factors that influence the propensity to travel: an individual's will to initiate events with members of one's social network, referred to as agency , and the social accessibility of network members themselves. Social accessibility defines a series of practical constraints for social-activity travel and agency defines the extent to which an individual will actively work within these constraints to maintain their social network. The theoretical section first unpacks these concepts while embedding them in the research literature, finishing with an operationalisation of agency and social accessibility. Using this theory, the empirical section investigates the relationship between agency, social accessibility, and factors associated with both the respondents and their personal networks. More specifically, we examine how agency levels of interaction are related to differences in demographics, global measures of network structure and composition, and measures of media use, particularly of Internet and telephone. We conclude that individuals who are proximate or more active are more likely to maintain reciprocal relationships, and that more distant or infrequent ties require greater maintenance on the individual's part. We believe that studies of activity-travel and ICTs will benefit from a theoretical lens that articulates some of the transformative effects of ICTs on travel vis-à-vis its effects on social life. Social accessibility and agency can help focus that lens thereby enabling researchers to make potentially more elaborate and realistic models that move beyond the spatial and temporal dimensions into social dimensions.
We describe an interview-based data-collection procedure for social network analysis designed to ... more We describe an interview-based data-collection procedure for social network analysis designed to aid gathering information about the people known by a respondent and reduce problems with data integrity and respondent burden. This procedure, a participant-aided network diagram (sociogram), is an extension of traditional name generators. Although such a diagram can be produced through computer-assisted programs for interviewing (CAPIs) and low technology (i.e., paper), we demonstrate both practical and methodological reasons for keeping high technology in the lab and low technology in the field. We provide some general heuristics that can reduce the time needed to complete a name generator. We present findings from our Connected Lives field study to illustrate this procedure and compare to an alternative method for gathering network data.
Abstract: A conceptual model of social activity-travel behaviour is described, incorporating an a... more Abstract: A conceptual model of social activity-travel behaviour is described, incorporating an activity-scheduling framework which explicitly includes the influence of the individual's social context. More explicitly, the model develops the concepts of social networks, activities, and social episodes, and defines the individual's social activity generation and spatial distribution in a context of his/her social networks. Also, empirical findings regarding the influence of social network characteristics on individual's socialising patterns are ...
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Papers by Juan Carrasco