Synthesizing Land Use and Transportation 

Accessibility measures the ease of reaching potential destinations, capturing the interaction between transportation infrastructure and land use. The measurement summarizes potential opportunities reachable from a given place, at a given time, traveling using a certain mode, for a certain amount of time. Also called Access to Destinations or Access to Opportunity, this set of metrics has been the focus of theoretical and empirical development in transportation research for fifty years. Recent advances in data availability and computing approaches, however, have led to an increase in variety and application of these metrics.

Traditional evaluation of transportation systems largely focuses on vehicle speed: where is speed low or constrained? Where is congestion causing delay? How many vehicles can move through a single point, or along a segment of roadway? This type of approach is mandated for federally funded (that is, nearly all) roadway projects, both in planning and prioritizing, and in studies of impact after infrastructure is built. What these measurements miss is twofold: whether the infrastructure changes lead to improvement in peoples’ ability to reach desired destinations in the short term, and what the land use changes resulting from the infrastructure mean for peoples’ ability to reach desired destinations in the long term. 

In this study, we describe how Accessibility metrics can help agencies: 

• Better measure short term changes in how opportunities for travel are provided
• Better understand where and for whom project investments will produce benefits
• Better predict what long-term land use changes are likely 

Together, these functions of Accessibility metrics mean performance evaluation, cost-benefit analysis, and other accountability measures can be applied more directly to what is under agency control.