TRAVEL BEHAVIOR-A SYNTHESIZED THEORY

This theory of household travel behavior in urban areas relates travel behavior directly to activities and activity site locations. As a result, the distribution and location of activity opportunities is a critical influence on the activity and travel pattern. The central process is adaptation, the effort to reduce the imbalance between current or expected needs and available opportunities. These adaptations form a hierarchy from small-scale travel or activity adjustments to major changes in residential or work location. Higher order adaptations develop only when lower-order changes do not sufficiently reduce the imbalance below some threshold. The major determinants of activity and travel patterns and of the trajectory of adaptations are: social class position, ethnicity, life cycle status, and residential location. These influence activity and travel patterns through several intervening factors: social roles, attitudes, resource constraints, social norms, and perceptions of opportunities. The resulting adaptive process leads to changes in behavior which, in turn, modify the intervening factors. Adaptations vary in stability but can be viewed as a continuous process due to new imbalances resulting from the same set of forces. The distribution, location, and form of activity sites and transportation systems are critical influences on activity and travel patterns. The spatial distribution of activity sites is broadly related to differences in urban area characteristics: residential densities, economic base, sociodemographic distribution, and historical development. These spatial variations help to clarify the travel and activity patterns of subgroups of the population: travel frequencies, travel distance, car ownership, and activity site locations. The specific forms of adaptation are influenced by these variations in metropolitan structure.