Suggested Citation:
Barbour, Elisa and Susan L. Handy (2019) Multi-Variable Relationships among Built-Environment Factors That Affect Vehicle Miles Traveled. Transportation Research Board 98th Annual Meeting

Many studies on the relationship of the built environment and travel behavior refer to the “D” variables to denote key aspects of the built environment associated with travel patterns, namely development density, diversity, street design, destination accessibility, and distance to transit. The Ds framework also has been incorporated into practitioner tools used to predict the travel impacts and associated environmental effects of projects and plans. Research using the Ds framework often assumes that the variables exert independent effects on travel, but the variables are, in fact, interdependent both conceptually and on the ground. Based on review of empirical research findings, this paper considers shortcomings of the common approach of evaluating D-variable effects independently in accounting for three aspects of the travel-built environment relationship: overlap effects (a.k.a. proxy effects) among built-environment variables, interactive effects (a.k.a. synergies, denoting situations when combined effects of variables exceed the sum of their independent effects), and locational effects evaluated at wider-than-local scales. Finally, the paper discusses research strategies that may compensate for shortcomings of the conventional approach.

Key words: Accessibility, built environment, highway design, literature reviews, population density, travel behavior, travel patterns, vehicle miles of travel