University of California Transportation Center

This dissertation addresses the question of how particular forms of metropolitan development affect travel patterns, a question long of concern to planners but recently the subject of a heated debate. Critics identify sprawling, low-density, single-use, automobile-dependent suburban development as the problem, and recommend a return to the higher-density, mixed-use, pedestrian-oriented design practices of the past as the solution, particularly as a way of reducing non-work automobile travel. Yet the question remains: can these “neo-traditional” communities reduce automobile travel when implemented within the broader context of freeways and regional shopping malls.

The concept of accessibility provides an important tool for resolving this question. Accessibility measures the attractiveness of potential destinations and the cost of reaching them. By measuring both the accessibility to activity within the community, or “local” accessibility, and the accessibility to regional centers of activity from that community, or “regional” accessibility, the structure of a community and its relationship to the metropolitan area are more fully characterized. It is hypothesized that, for shopping trips, high levels of accessibility are directly associated with shorter distances and greater variety in destinations and indirectly associated with greater frequencies and some shift away from automobile use. Some degree of substitutability between local and regional accessibility is also hypothesized, suggesting that high levels of local accessibility may reduce the need for regional travel.

This dissertation defines quantitative and qualitative measures of local and regional accessibility and uses them to test the implications for shopping travel of alternative forms of development in a case study of the San Francisco Bay Area. An aggregate-level analysis shows a significant negative relationship between the length of the shopping trip and both local and regional accessibility, but no significant relationship with trip frequency. Accessibility is more thoroughly evaluated both quantitatively and qualitatively for four Bay Area communities, leading to several refinements in the definition and measurement of local and regional accessibility. A survey of residents in the case study areas reveals a more complex relationship, in that high levels of accessibility work to both decrease and to increase travel. The survey also shows that substitutability is limited: local accessibility seems to have little effect on regional travel. This dissertation concludes by reviewing policy implications, particularly the importance of finding an appropriate balance between the sometimes conflicting goals of minimizing travel and maximizing the range of alternatives available to residents.