The Interaction Effects in the Relationship Between Urban Form and Sustainable Transportation

Abstract

The relationship between urban form and sustainable transportation has been extensively explored in the existing literature, and it is generally accepted that an urban form characterized by higher density, mixed land use pattern and higher accessibility could shorten travel distance and encourage people to choose alternative non-auto travel modes, which in turn reduces the fuel consumption and associated GHG emissions. However, the extensive research on urban form and sustainable transportation has only identified significant correlations between individual urban form variables, such as urban density, land use mix or road connectivity and the one or multiple sustainable transportation outcomes, such as travel mode or vehicle miles travelled (VMT), but very limited empirical studies have been identified to examine the interaction effects that may exist between the urban form attributes. This paper proposes the hypothesis that interaction effects exist between urban form attributes when examining their influences on sustainable transportation. Taking all cities in Florida, U.S. as a case, the interaction effects in the relationship between urban form and sustainable transportation are tested with empirical data. The regression results verified our hypothesis that density shows “threshold negative-to-positive” synergy with other urban form variables, indicating that certain theoretical correlations between urban form variables and sustainable transportation outcomes are conditional depending on the interactions between or among urban form attributes. The results may expand the theoretical framework on the topic of land use and transportation and has considerable policy implications for planning support systems.