A Subjective Measure of Car Dependence

TitleA Subjective Measure of Car Dependence
Publication TypeJournal Article
Year of Publication2011
AuthorsZhao J
JournalJournal of the Transportation Research Board

A subjective measure of car dependence was developed on the basis of people's own assessment of their reliance on car use. The measure supplements the commonly used objective measure on the basis of actual car use. Structural equation models (SEMs) were estimated to quantify the subjective dependence and to examine its determinants: demographics, socioeconomics, and land use and transit access. The comparison between subjective dependence and actual car use disclosed significant differences between the measures, despite their statistical linkage. The measures also differed significantly in terms of how they were influenced by the determinants. Segmenting the population by both measures revealed 20% of the sample with contrasting subjective and objective measures. After controlling for the determinants, the SEMs examined relations between subjective car dependence (attitude), actual car use (behavior), and the intent to reduce car use (intention). Given the cross-sectional nature of the data, causality could not be proven. Two plausible structural relationships were tested: that actual car use determined subjective car dependence and that no direction of causality was assumed. Subjective car dependence mediates the impact of car use on the intent to reduce it: the direct effect of car use on the intent to reduce it is 0.2; the indirect effect through stated car dependence is -0.6; the total effect is -0.4. Actual car use explains approximately 50% of the variation in subjective car dependence, which, together with actual car use, explains approximately 60% of the variation in people's intent to reduce car use.