Interstate 640 (abbreviated I-640) is a bypass of Interstate 40 running north of Knoxville, Tennessee. The route serves as an alternative for traffic going east on Interstate 40 intending to turn northward on Interstate 75, which has greatly relieved congestion in downtown Knoxville.
I-640 begins at an interchange with I-40 and I-75, where I-75 continues onto I-640. Initially heading northwest, I-640 and I-75 turn northeast, intersecting SR 62 before coming to an interchange with SR 9, US 25W, I-75, and I-275. As the freeway continues, US 25W and SR 9 run concurrently for the rest of its length. I-640 interchanges with SR 33 and US 441, as well as one providing access to the East Towne Mall. The highway then turns south and terminates at I-40.
For many years only about a 2 miles (3.2 km) segment between State Route 33 (Broadway/Old Broadway exit) and U.S. Highway 25W (Clinton Highway exit) was open. Then in 1981, the road was finally completed in anticipation of the traffic which was to be generated by the 1982 World's Fair. Then Governor of Tennessee, now United States Senator Lamar Alexander officially opened the road by walking its entire length dressed in his famous red plaid shirts that he famously wore during his both of his campaigns for Governor of Tennessee. In May 2008, a complete redesign near I-40 east of downtown added lanes, reconfigured exits, and improved safety closed that section of I-40 for 13 months. The road construction project was officially called Smart Fix 40, and the Tennessee Department of Transportation closed that section of I-40 until June 2009, when it was officially completed 18 days early. During the course of the Smart Fix 40 construction project, the Tennessee Department of Transportation used I-640 as the official detour route for I-40 traffic during the time in which I-40 was closed for the reconfiguration.