Travel Choice with No Alternative

Abstract

Land use is expected to have a two-tiered effect on reducing automobile dependence. One is to enhance access to choices and the other to influence modal shifts away from driving. Existing studies have focused primarily on the second-tier effect. This article presents an empirical study of automobile dependence with emphasis on the identification of the first-tier effect. Using the Boston 1991 activitytravel survey data, the study jointly models travel choice set formation and mode choice decision. Automobile dependence is defined and measured as the probability that a traveler has the automobile as the only element in the choice set of travel modes. The study finds a wide variation in levels of automobile dependence along spatial and social dimensions. Elasticity estimates show that automobile dependence is highly sensitive to street network connectivity and to automobile availability, while population/job density and transit supply also matter. The study confirms the choice-enabling role of land use in reducing automobile dependence.