This study sets forth the hypothesis that the effects of automobile ownership on household trip generation and automobile utilization are diminishing in the United States. The reasoning behind this statement is that, as motorization progressed and automobile ownershipbecame widespread in the United States, the strong association between a household's propensity to travel and its automobile ownership, which existed in earlier stages of motorization, diminished. Therefore trip making of households can no longer be effectively explainedby their level of automobile ownership. This study extends previouswork of the authors in which automobile ownership effects were found to be decreasing for nuclear-family households. The relationships between household automobile ownership and a number of travel pattern indicators are examined in this study for all households containedin the 1963 and 1974 origin-destination survey results from Rochester, New York. Statistical analyses of the trip records indicate thatthe ability of automobile ownership to explain variations in the travel indicators has diminished over time and automobile ownership isno longer a key descriptor of household trip making. The cross-classification scheme based on household size and automobile ownership is also shown to have lost its effectiveness in household trip generation analysis. A more extensive categorization of household composition, however, has retained its explanatory power for the total number of trips generated by a household.(A).
Abstract