Interstate 175 (I-175) was a proposed Interstate highway to relieve traffic along the I-75 corridor. House Report 107-108 in the US Representatives report, details the proposed spending of the US Department of Transportation for FY2002, which includes $2,400,000 for the Interstate 175 corridor. This includes the feasibility and the planning study.
This road would start at I-75 in Chattanooga, Tennessee to I-75 in Lexington, Kentucky (shortening the south–north route), bypassing Knoxville. This highly impractical route (if ever built) would be expensive, since the proposed route passes through much mountainous terrain. Tunnels would be needed to go underneath several high mountain ridges. The proposed highway would cost in excess of $3,000,000,000. Despite having an odd prefix, this route will be more of a loop than a spur as most odd prefixes for 3-digit interstate routes imply a spur away from the highway.
The I-175 designation may not last for long if I-59 employs this segment in the future for extension.