This dissertation examines the psychological factors that influence travel behavior such as people's personality traits, environmental attitudes, car pride and perceptions of convenience and comfort. Despite the recognition of the importance of these psychological factors in better understanding travel behavior, transportation agencies have failed to integrate them into planning practice and policy debate in the quantitative way. This dissertation reflects on this failure, identifies the barriers that have contributed to it, and reviews innovations in travel behavior research which may help overcome these barriers. This dissertation proposes a structure for analyzing traveler preferences that incorporates these psychological factors into travel behavior analysis. A set of eight factors are presented as the latent elements of travel preferences to illustrate the structure, including two personality traits; three environmental attitude factors and car pride; and two perceptual factors of convenience and comfort. A MIMIC model quantifies the eight factors and examines the relationships among these factors as well as between them and socioeconomic variables. Despite the significant correlations with socioeconomic variables, personality, attitudes and perceptions prove to be characteristics of individuals that are distinct from the socioeconomics. The dissertation presents three applications that incorporate these latent factors into travel demand analysis of three critical aspects of travel behavior: car use, mode choice and car ownership. Incorporating the latent variables significantly improves the overall exploratory power of the transportation models.(cont.) The results suggest that plausible changes in traveler preferences can have an effect on behavior in magnitude similar to the impacts that result from rising household income or increased population density. Unobserved heterogeneities exist not only for preferences with respect to observed variables such as travel time, but also for latent factors such as car pride and perception of convenience. Preference Accommodating and Preference Shaping in Transportation Planning 3 Mutual dependencies between travel preferences and behavior are identified and the direction and strength of the causal connections are modeled explicitly. Depending on the specific latent factors and aspect of travel behavior, the causal relationships could be from preferences to behavior, from behavior to preferences, or be significant in both directions concurrently These three applications also demonstrate in terms of methodology that 1) hierarchical relationships among latent factors can be simultaneously estimated with discrete choice models; 2) latent variable and latent class modeling techniques can be combined to test unobserved heterogeneities in travelers' sensitivity to latent variables; 3) causal relationships between behavior and preferences can be examined in the SEM or hybrid SEM and discrete choice model. This dissertation proposes two complementary perspectives to examine how to embed traveler preferences in the planning practice: planning as preference accommodating and planning as preference shaping.(cont.) Combining both perspectives, this dissertation argues that by ignoring the importance of traveler preferences, not only may we make serious mistakes in the planning, modeling and appraisal processes, but we may also fail to recognize significant opportunities to mitigate or solve transportation problems by influencing and exploiting changes in people's preferences.

Dissertation Committee: Joseph Ferreira, Jr., Nigel Wilson, Ralph Gakenheimer and Joan Walker.