Risk-based framework using geographic information systems to identify transportation corridors vulnerable to development

The Virginia Department of Transportation (VDOT) is increasingly involved with the land development process in evolving transportation corridors. This process includes consideration of real estate interests, rezoning and permitting approvals, site plans, public utilities, right of way, access management, and the transportation facilities themselves. Localities may compete with one another for economic development and withhold plans for developing corridors or may simply be unaware of development intentions. It is therefore important that VDOT transportation planners anticipate and proactively address future development along corridors to avoid surprise, regret, and belated action. With many thousands of miles of undeveloped corridors across the Commonwealth, VDOT must prioritize the corridors and corridor sections most in need of immediate attention. This study developed a comprehensive approach using geographic information systems (GIS) to identify and prioritize the needs for protection strategies in countywide corridors. Over eighty GIS data layers sourced from VDOT, Fauquier County, and others were evaluated to determine appropriate factors for the analysis. Layers not available to other counties were ruled out. Layers were selected by adopting principles of risk management, asking experts about the flaws and consequences in corridor protection. Four indicator factors including lateral distance from corridors, proximity to intersection of corridors, proximity to population centers, and proximity to employment centers were used in the analysis to identify parcels with a high likelihood of development. Two constraint factors including protected parcels and economically developed parcels were used to identify very low likelihoods of development and eliminate parcels from the analysis. Several corridor sections were identified as candidates for further study of protection strategies including early right-of-way acquisition and access management. The density of curb cuts and the average parcel values and development likelihoods were plotted against the centerline mile to suggest the opportunities and costs of risk management. The methodology aims to generate maximum insight by using a manageable number of GIS layers and is repeatable in other cities, counties, and regions of Virginia by using currently available data. The suggested training material for the GIS analysts is (1) the PowerPoint presentation initially developed for the steering committee, and (2) the sample GIS layers and associated files that were used for the Fauquier County case study. Both are available for download at www.virginia.edu/crmes/corridorprotection. The results (relative prioritization of corridor sections) are not dependent on assumptions or steps that may differ from analyst to analyst. In the future, a web- or spreadsheet-based implementation of the layer combination process could be developed for use in presentations and public meetings. The results will help VDOT make the business case for corridor protection, for example, considering cost-effectiveness, return on investment, multiple objectives and stakeholders, and/or cost-benefit ratio. The results (maps of priorities) should highlight the features that confirm and reject the intuition of the planner and analyst. Numerous examples of such insights gained in discussion of the results with Fauquier County planning staff and the steering committee are included in this report.