The correlational and causal investigation into the land use-transportation relationships: evidence from the Dallas-Fort Worth metropolitan area

The role of land-use and related policies in reducing automobile dependence has been the subject of heated policy debate for over two decades. Previous research has shed light on the correlations between land-use and travel. Yet a crucial knowledge gap still exists in establishing causality between the two. Do changes in land-use characteristics cause behavioral changes in individuals?????? decisions on what transportation means to use for travel? How does land-use as a contextual factor shape the decision process and outcome of trip frequency and travel mode choice? These questions remain largely unanswered. Attempting to fill the gap, this study applied the directed acyclic graphs method to identify the causal relationship between land-use and travel in the 9-county Dallas- Fort Worth (D-FW) metropolitan area. The logit captivity (LC) model, an extension to the conventional multinomial logit, was utilized to capture the contribution of land-use in affecting individuals?????? decisions on travel mode choice. All the data for this study were obtained from the North Central Texas Council of Governments (NCTCOG). Evidence from the D-FW region confirms to a certain extent the causal effects of land-use on travel. For work trips, increases in regional accessibility, job density and share of commercial land-use reduce the use of automobiles. Higher regional accessibility, however, causes households to generate automobile trips and thus leads to the increase in vehicle miles of travel (VMT). For non-work trips, population density, job density and regional accessibility are direct causes of the choice of automobile, while only regional accessibility is causally connected to reducing automobile trips and VMT. The logit captivity model results indicate that land-use contributes to captive-driving choices for home-based work trips. Lack of land-use mix at trip origins increases the probabilities of trip-makers being captive to the automobile from 0.06% to 5.62% for driving-alone and from 0.38% to 3.55% for shared-ride.