The Appalachian Development Highway System (ADHS) is a 3,000 miles, 13-state system of highways authorized by Congress to generate economic development in previously isolated areas, connect Appalachia to the interstate system, and provide access to areas within the Region as well as to markets in the rest of the nation. Currently, 86 percent of the AHDS is either complete or under construction. However, many of the remaining miles will be among the most expensive to build. The Appalachian Regional Commission (ARC) therefore commissioned the study to asses the economic development benefits of completing that system.
Since the AHDS was designed to generate economic development by linking isolated areas, ARC staff realized that the benefit analysis process must focus on the value of enhancing transportation connectivity, access to larger markets and intermodal connections. After reviewing alternative economic models, TREDIS was selected because of its unique ability to assess those access and connectivity factors and their economic consequences.
The project team consisted of Cambridge Systematics with HDR and EDR Group. The team utilized a national highway network provided by FHWA's Freight Analysis Framework (FAF) system, together with a detailed dataset on commodity flows for Appalachian counties that was developed by Wilbur Smith Associates and the Rahall Appalachian Transportation Institute at Marshall University. Additional GIS data was obtained to represent the extent of road system slope and curvature in mountain areas, where a slow vehicle can lead to significant traffic backups due to lack of passing lanes. TransCAD software was then used to model freight and passenger flows to, from, within and through the Appalachian Region. It was also used to estimate access to markets, airports, marine ports, intermodal rail, national borders and international gateways from each Appalachian county -- both current and projected upon completion of the ADHS.
TREDIS, the Transportation Economic Development Impact System., was applied to use the TransCAD results and estimate impacts on productivity, business attraction, economic growth and benefit-cost results for the Appalachian region and the nation. The final report (Economic Benefits of ADHS Completion) was issued in June 2008 and is available on the ARC website.