thumb|right|ADHS signs for [[U.S. Route 78/Alabama State Route 4/ADHS Corridor X with their distinctive blue color. Most other states do not have distinctive highway shields for ADHS, however.]]
The Appalachian Development Highway System (ADHS) is a series of highway corridors in the Appalachia region of the eastern United States. The routes are designed as local and regional routes for improving economic development in the historically isolated region. It was established as part of the Appalachian Regional Development Act of 1965, and has been repeatedly supplemented by various federal and state legislative and regulatory actions. The system consists of a mixture of state, U.S., and Interstate routes. The routes are formally designated as "corridors" and assigned a letter. Signage of these corridors varies from place to place, but where signed are often done so with a distinctive blue-colored sign.
The Appalachian Regional Commission (ARC) forecast benefits of ADHS' completion by FY 2045 as the creation of 47,000 new jobs and $4.2 billion in gross regional product (GRP).
The PARC report and the Appalachian governors placed top priority on a modern highway system as the key to economic development. As a result, Congress authorized the construction of the Appalachian Development Highway System (ADHS) in the Appalachian Development Act of 1965. The ADHS was designed to generate economic development in previously isolated areas of the 13 Appalachian states, supplement the interstate system, and provide access to areas within the region as well as to markets in the rest of the nation.
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|1998
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|$8.5 B
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|2013
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|$11.4 B
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|2023
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|$9.7 B To evaluate the effectiveness of such investments, land change modeling was used to compare 1976 "pre-" and 2002 "post-" highway conditions. The study focused on Ohio's SR-32 portion of Corridor D and the 15 counties in close proximity; Adams, Athens, Brown, Clermont, Gallia, Highland, Hocking, Jackson, Meigs, Morgan, Pike, Ross, Scioto, Vinton, and Washington Counties. Using data acquired from the Landsat system of earth observational satellites, the comparison revealed slight, yet significant, levels of urban expansion within a band surrounding the new highway. Beyond this band land use was more stable, indicating even minor distance increases from the highway reduced the likelihood of further development. Case study excerpts from five corridors were:
- Corridor B (North Carolina and Tennessee). Though in total, this case study focused on the segment of Corridor B completed in 2003, passing through the Blue Ridge Mountains to connect western North Carolina with northeastern Tennessee. This project enabled improved access to the Port of Charleston and new residential and commercial developments near Weaverville, North Carolina. The highway led to a direct increase of around 4,600 new jobs in the area. The 2021 ADHS Cost-to-Complete Estimate Report reiterated previous compilations that construction investments made between 1965–2015 contributed to the annual generation of over $19.6 B additional Appalachian business sales, representing $9+ B added GRP. Usage of the ADHS was saving 231 million hours of travel time annually, equivalent to a $10.7 B savings in transportation costs and worker productivity per year.
|established=
|location=Sandy Springs, GA – Clyde, NC
Corridor A is a highway in the states of Georgia and North Carolina. It travels from Interstate 285 (I-285) north of Atlanta northeast of I-40 near Clyde, North Carolina. I-40 continues east past Asheville, where it meets I-26 and Corridor B.
In Georgia, Corridor A travels along the State Route 400 (SR 400) freeway from I-285 to the SR 141 interchange southwest of Cumming. From here to Nelson, near the north end of I-575, Corridor A has not been constructed; its proposed path is near that of the cancelled Northern Arc. It begins again with a short piece of SR 372, becoming SR 515 when it meets I-575. SR 515 is a four-lane divided highway all the way to Blairsville. From Blairsville to North Carolina, the corridor has not been built, and SR 515 is a two-lane road.
The short North Carolina Highway 69 (NC 69) takes Corridor A north to U.S. Route 64 (US 64) near Hayesville. Corridor A turns east on US 64, and after some two-lane sections, it becomes a four-lane highway. Corridor A switches to US 23 near Franklin, and meets the east end of Corridor K near Sylva. From Sylva to its end at I-40 near Clyde, Corridor A uses the Great Smoky Mountains Expressway, which carries US 23 most of the way and US 74 for its entire length.