Ifigenia Psarra

Modeling Context-Sensitive, Dynamic Activity Travel Behavior by Linking Short- and Long-Term Responses to Accumulated Stress: Results of Numerical Simulations

As existing activity-based models of travel demand simulate activity travel patterns for a typical day, dynamic models simulate behavioral response to endogenous or exogenous change along various time horizons. Prior research predominantly addressed a specific kind of change, which usually affected a specific time horizon. In contrast, the current study aims to develop a dynamic model of activity travel decisions that links short- and long-term adaptation decisions in a hierarchical manner. Specifically, this study focuses on the bottom-up process of influence, in which problems with rescheduling on a daily basis may induce a long-term change. The authors assume that travelers will first explore short-term adjustments of their habitual activity travel patterns so as to cope with change and increasing stress. Only when travelers recognize that such adaptation strategies are ineffective will they consider long-term decisions. The proposed framework integrates three key concepts: aspiration, activation, and expected utility. Moreover, both rational and emotional mechanisms are taken into account. The study demonstrates model properties by using numerical simulation. Individual travelers are represented as agents, each with their cognition of the environment, habits, preferences, and aspirations. The results offer insight into the dynamics of traveler learning–adaptation and into the evolution of long-term decisions.

Simulating choice set formation processes in a model of endogenous dynamics of activity-travel behavior: the effect of awareness parameters

Models of activity-travel behavior can be a useful tool in order to predict the direct or secondary effects of various spatial, transportation or land-use policies. Whereas existing activity-based models of travel demand focus on a static, typical day, dynamic models simulate behavioral response to endogenous or exogenous change, along various time horizons. The current study focuses on modelling endogenous dynamics of activity-travel behavior. Endogenous dynamics are triggered by stress, which is regarded as dissatisfaction with current habits. It is assumed that people try to alleviate stress by conducting short-term changes, within or beyond their current choice sets. If these attempts prove to be unsuccessful, they may also consider long-term changes, such as moving to a new residence, and buying a car. In this study, this self-improvement process, which can result in both short and long-term adaptations, is modeled. In the proposed framework, choice set formation and the key concepts of aspiration, activation, awareness and expected utility are integrated, while both rational and emotional mechanisms are taken into account. Numerical simulations are conducted in order to check the face validity of the model, as well as the impact of awareness parameters on choice set formation and on the overall system behavior.

The effect of emotional responses on endogenous dynamics of activity-travel behavior : numerical simulation results

Abstract The current study aims at developing a model of endogenous dynamics of activity-travel behavior. Endogenous dynamics are induced by stress, which is regarded as dissatisfaction with current habits. It is assumed that people try to alleviate stress by hierarchically trying short-term and then long-term adaptations. In the proposed framework, choice-set formation and the concepts aspiration, activation, awareness and expected utility are integrated, while both rational and emotional mechanisms are taken into account. Numerical simulations are conducted in order to check the face validity of the model, as well as the impact of affective responses on system performance.

Incorporating bounded rationality in a model of endogenous dynamics of activity-travel behaviour

Abstract Purpose This chapter discusses the formulation of an agent-based model to simulate day-to-day dynamics in activity-travel patterns, based on short and long-term adaptations to exogenous and exogenous changes. Theory The model is based on theoretical considerations of bounded rationality. Agents are able to explore the area, adapt their aspirations and develop habitual behaviour. If they experience dissatisfaction, stress emerges and this may lead to short or long-term adaptations of an agent’s activity-travel patterns. Both cognitive and affective responses are taken into account, when agents evaluate available options. Moreover, memory-activation and forgetting processes play a significant role in the development of habitual behaviour. Findings Results of numerical simulations show the effect of memory-activation and emotion-related parameters on habit formation, on the decision-making process and on overall model behaviour. Effects of specific aspects of bounded rationality on the evolution of dynamics in the activity-travel patterns of an individual are illustrated. Effects seem realistic, behaviourally rich and, therefore, more sensitive to a larger spectrum of policies. Originality and value The model is unique in its kind. It is one of the first attempts to formulate a dynamic model of activity-travel behaviour, based on principle of bounded rationality, which includes both cognitive and affective mechanism of adaptation.

THE EFFECT OF STRESS TOLERANCE ON DYNAMICS OF ACTIVITY–TRAVEL BEHAVIOR: NUMERICAL SIMULATION RESULTS

The primary and secondary effects of various spatial and transportation policies can be evaluated with models of activity–travel behavior. Whereas existing activity-based models of travel demand simulate a typical day, dynamic models simulate behavioral response to endogenous or exogenous change, along various time horizons. The current study aims at developing a model of endogenous dynamics of activity–travel behavior. Endogenous dynamics are induced by stress, which is regarded as dissatisfaction with current habits. It is assumed that people try to alleviate stress by trying short-term changes, within the options known to them or by exploring new options. If these explorations prove to be unsuccessful, they will consider long-term changes, such as moving to a new residential location, buying a car, etc. Therefore, this self-improvement process can result in both short and long-term adaptations. In the proposed framework, choice-set formation is modeled, the key concepts of aspiration, activation, awareness and expected utility are integrated, while both rational and emotional mechanisms are taken into account. Numerical simulations are conducted in order to check the face validity of the model, as well as the impact of stress tolerance parameters on system performance.

Short-Term Adaptations as a Response to Travel Time Increases: Results of Stated-Adaptation Experiment

This study focused on short-term dynamics of activity-travel behavior as a response to travel time increases. It is assumed that short-term changes are triggered by stress, which is defined as the deviation between an individual’s aspirations and his or her daily experiences. When stress exceeds a tolerance threshold, habitual behavior is dissociated, and various adaptation strategies emerge. A stated-adaptation experiment was designed to trace behavioral change. The analysis results of the empirical data corresponding to travel time scenarios are presented. Specifically, a random coefficient logit (binary) model that focused on the decision of activating a short-term change was estimated. Next, a random parameters (mixed) logit model is presented; it indicates which specific activity attribute is adjusted once a short-term adaptation is chosen. Then one random coefficient logit (binary) model indicates whether an exploitation of the existing choice set or an exploration effort occurs once an activity attribute is chosen to be adapted. These analyses led to interesting results about the inertia characterizing people’s behavior and their unwillingness to deviate from their habitual state. In addition, it is seen that richer choice sets lead to more short-term changes and specifically to more exploitation efforts. Moreover, heterogeneity plays a significant role in all these models. Finally, the effect of stress as well as of various sociodemographic and travel-specific variables (activity type, destination location, transport mode, and day of the week) is revealed and can be taken into account in the design of spatial and transportation policies.