Transportation ecoefficiency: quantitative measurement of urban transportation systems with readily available data

In this study, the concept of transportation ecoefficiency (TE) is described, and it is argued that this concept offers coherence to theoretical discussions of the environmental impact of transportation. A TE measure using readily available data is proposed, with four components: (1) percentage of commuters driving to work; (2) percentage of commuters taking public transit; (3) percentage of commuters walking or riding a bicycle; and (4) population density. A confirmatory factor analysis suggests that these components are useful for measuring TE and consistent in their relationships over time. This TE index is used to analyze TE in metropolitan areas in the United States (1980-2008) and in the United Kingdom (1981-2001): TE is decreasing in both countries despite very different starting points, with worrisome implications for climate change and other transportation-related environmental impacts. The paper concludes with a discussion of some uses for the TE metric in empirical research and planning practice, and how the concept could enhance the literature on transportation and the environment.