International Choice Modelling Conference, International Choice Modelling Conference 2015

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A Two-Stage Choice Model for Daily Activity Patterns with Dynamic Choice Sets
Siyu Li, Francisco Camara Pereira, Der-Horng Lee, Moshe Ben-Akiva

Last modified: 18 May 2015


(Short Abstract) 

In the context of activity-based modeling, the concept of daily activity pattern is crucial to distinguish between activity-based and tour-based demand models. In this work, we explore a probabilistic context free grammar (PCFG) based representation of daily activity patterns within the framework of discrete choice modeling. We define a daily activity pattern as a sequence of activities and propose a two-stage choice model for daily activity patterns where a choice set is stochastically customized for each individual based on social-demographic variables and accessibility measurements, followed by a discrete choice model to determine the chosen pattern.

In the first stage, PCFGs are used to characterize the structures and deterministic distributions of daily activity sequences. The choice set is then generated by repeated weighted sampling from a universal set with infinite number of activity patterns. The weights are generated for each individual-specific probabilistic context-free grammar and are influenced by social-demographic variables and accessibility of different activities. The proposed two-stage model is shown to be able to replicate the patterns observed in the data for verification. Moreover, without pre-specified and fixed choice set for daily activity patterns, the stochastic choice sets generated in the first stage will evolve dynamically with the change of social-demographic characteristics of an individual and network performance. Thus, the proposed model can be applied to policy scenarios where new patterns are expected to emerge from the development and upgrade of infrastructure and transportation systems. In the second stage, the stochastic choice sets generated is applied in discrete choice models. While the stochastic choice sets require a flexible choice structure for the choice model, we are able to take correlations among alternatives into consideration with several model formulations.

We believe that the proposed two-stage model has potentials in activity-based modeling and policy decision making as the development in infrastructure and transportation systems will be reflected in the change of weights and evolve the choice set gradually, which will eventually be captured by the choice model.

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