In the United States, future Interstate Highways include proposals to establish new mainline (one- and two-digit) routes to the Interstate Highway System. Excluded from this article are auxiliary Interstate Highways (designated by three-digit numbers) in varying stages of planning and construction, and the planned expansion of existing primary Interstate Highways. Congressionally designated future Interstates Several Congressional High Priority Corridors have been designated as future parts of the Interstate Highway System by the Intermodal Surface Transportation Efficiency Act and amendments. By law, they will become interstates when built to Interstate standards and connected to other interstates. Interstate 3 Interstate 3 is the proposed designation of an Interstate Highway Corridor under development in the Southeastern United States. It is planned to run from Savannah, Georgia, to Knoxville, Tennessee. Its number does not follow standard numbering conventions; under established numbering conventions, I-3 would normally run west of I-5 along the Pacific Coast. The unnumbered Interstate was established by the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU) legislation that also provided for Interstate 14. The "Interstate 3" designation has not been officially accepted by American Association of State Highway and Transportation Officials (AASHTO) or the Federal Highway Administration (FHWA), but is being used by the Georgia Department of Transportation and others to identify the highway. The number comes from the 3rd Infantry Division which is based in Georgia. Portions of the planned route, including the Savannah River Parkway, are already built to Interstate standards; the exact route has not been finalized, especially across the Appalachian Mountains northwest of Augusta, Georgia. Interstate 7 or 9 Interstate 7 or Interstate 9 has been proposed by Caltrans for State Route 99 in central California. It would go from the split with I-5 at Wheeler Ridge (Wheeler Ridge Interchange) north through Bakersfield and Fresno to Stockton, where the proposed route turns west via the State Route 4 freeway to a terminus at I-5 in the central part of that city. An alternate proposed terminus is located at the I-5/US 50/Capital City Freeway junction in Sacramento, where the future Interstate, after continuing north from Stockton along Route 99, can turn west along the Capital City Freeway, already an Interstate route (unsigned I-305), to connect with I-5, which extends north toward Redding. This also serves as a connector to the existing northern portion of Highway 99. The future Interstate's prospects for development to appropriate standards