Latent modal preferences, or modality styles, are defined as lifestyles built around the use of a particular travel mode or set of travel modes. Traditional models of travel mode choice assume that all individuals are aware of the full range of alternatives at their disposal, and that a conscious choice is made based on a tradeoff between perceived costs and benefits associated with the level-of-service attributes of different travel modes. Though such a representation is convenient from the standpoint of model estimation, it is oblivious to the influence of inertia, incomplete information and indifference, reflective of more deeply entrenched individual variations in preferences, attitudes and lifestyles.
This talk presents a latent class choice model (LCCM) framework that explicitly captures the relationship between modality styles and travel mode choice. The framework is applied to an analysis of travel behavior of approximately 25,000 individuals in the San Francisco Bay Area. The study identifies six distinct modality styles in the sample population that differ from each other in terms of their taste parameters and choice sets. Most notably, nearly a third of the sample population is found not to consider any mode other than the automobile when deciding how to travel. The study finds that travel mode choice models that do not account for the influence of modality styles can bias travel demand forecasts by as much as 20-30%. Ongoing and future research will extend the model framework to reflect the pervasive influence of modality styles on other dimensions of individual and household travel and activity behavior.