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 and runs approximately north of downtown through the northern neighborhoods of Knoxville. For its first , I-640 has a concurrency with I-75, although exits along this segment are numbered according to the former's mileage. For the rest of its length, the Interstate maintains an unsigned concurrency with U.S. Route 25W (US 25W). Both of these highways were rerouted from their original alignments upon I-640's completion. The route that is now I-640 was first planned by the city of Knoxville in 1945 and initiated by the Federal Aid Highway Act of 1956, along with most of the Interstate Highway System. Initial construction work began in the early 1960s, and for many years, only of the highway was open to traffic. Work on the remainder of I-640 began in 1977, and the last section was completed in 1982. Route description I-640 has three lanes in each direction for its entire length, in addition to auxiliary lanes between some interchanges. Annual average daily traffic (AADT) counts range from approximately 69,000 vehicles per day at the highway's eastern terminus more than 94,000 vehicles on the western leg. Unlike the other Interstate Highways in Knoxville, however, I-640 rarely experiences severe congestion. I-640 begins west of Downtown Knoxville at a directional T interchange with I-40 and I-75, where the latter continues onto a concurrency with I-640. Along this section, I-640 is treated as the primary route, with exits numbered according to its mileage. Initially heading northwest, the interstate immediately passes under State Route 169 (SR 169, Middlebrook Pike) without an interchange. A short distance beyond this point, the highway turns north and crosses a CSX railroad mainline, intersecting with SR 62 (Western Avenue) in a partial cloverleaf interchange a short distance later. It then veers northeast into the southern fringes of Dutch Valley, running along the northern base of Sharp's Ridge. About later, I-640 reaches an unusual three-level combination interchange, commonly known as the Sharp's Gap Interchange, with US 25W (Clinton Highway), I-75, and the northern terminus of I-275. A series of towering radio masts on Sharp's Ridge dominate the view to the