For decades, the Appalachian Development Highway System (ADHS) has been viewed as one of the most significant long-term infrastructure investments supporting economic opportunity in Appalachia. As more than 92 percent of the system has been completed, open to traffic or under construction as of 2026, the question is no longer simply what benefits completion may generate in theory, but what outcomes have been realized in places where corridors have operated for years or decades. This research report, commissioned by the Appalachian Regional Commission addresses that question through in-depth case studies of four completed or substantially completed corridors:

• Corridor B (US-23) in eastern Kentucky,
• Corridor E (I-68) in western Maryland,
• Corridor T (I-86) in southern New York, and
• Corridor V in Alabama and Mississippi.

The report concludes that completed ADHS Corridors can play a critical economic development role by opening up new opportunities in manufacturing, logistics, tourism, and related sectors.  The greatest impacts of ADHS corridors have often been realized when highway access intersects with strategic assets, such as industrial clusters, multimodal transportation and logistics networks, workforce resources, tourism destinations, and proactive development efforts.  Together, these case studies illustrate that while outcomes vary by region, completed ADHS corridors still generate meaningful economic benefits for surrounding regions and provide a foundational platform for diversified and opportunity-driven economic development.