The following highways are numbered 640:
| Preceded by 639 | Lists of highways 640 | Succeeded by 641 |
Interstate 640 (I-640) is an east–west auxiliary Interstate Highway in Knoxville, Tennessee. It serves as a bypass for I-40 around Downtown Knoxville and is also an alternative route for traffic passing between I-40 and I-75. All trucks carrying hazardous cargo through Knoxville are required to use I-640. It has a total length of 10.80 miles (17.38 km) and runs approximately three miles (4.8 km) north of downtown through the northern neighborhoods of Knoxville.
State Route 640 is an east–west state highway in the northeastern portion of the U.S. state of Ohio. SR 640 has its western terminus is at a signalized intersection with SR 283 in Willowick. Its eastern terminus is in downtown Willoughby at a signalized intersection where it meets US 20 and SR 174, the latter of which has its northern terminus at this same intersection.
State Route 169 , also known as Middlebrook Pike, is a west-to-east secondary highway in Knox County in the U.S. state of Tennessee.
State Route 6 (SR 6) is a state highway that is unsigned. It travels through the central part of the U.S. state of Tennessee from Lawrence County to Sumner County. The highway is related to the following U.S. Highways:
