U.S. Route 129 in Tennessee

State Route 115 (SR 115) is the hidden state route that overlaps the entire route of US 129 in the state of Tennessee. The highway is 52.8 miles (85 km) long and is located entirely in East Tennessee. It begins in Blount County and ends in Knox County. It is completely unsigned, with the exception of mileposts, with the highway being solely signed as US 129.

The J. E. "Buck" Karnes Bridge over the Tennessee River

The Alcoa Highway portion of US 129 was first constructed and completed as a two-lane roadway from Knoxville to Blount County in 1939 to provide access to the then recently opened McGhee Tyson Airport. US 129's bridge over the Tennessee River in Knoxville was completed in 1935, and was named after James Ernest Karnes (a.k.a. J. E. "Buck" Karnes), a Knoxville recipient of the Medal of Honor. By 1963, Alcoa Highway was widened into a four-lane median-divided facility between I-40 and McGhee Tyson Airport. Several upgrades improving mobility were constructed on the Knoxville-Knox County section of Alcoa Highway, including replacements of at-grade intersections with interchanges at the University of Tennessee Medical Center (UTMC) and John Sevier Highway in the mid-1970s and mid-1980s respectively.[2]

Increasing congestion on Alcoa Highway in Knoxville prompted pushes from residents to form a neighborhood group Make Alcoa a Safe Highway (MASH) in the early 1980s, seeking to address concerns of safety on the highway. In 1986, MASH issued a report with immediate request and short and long-term range plans. Several of the recommendations were established such as a ban of parking on the US 129's right-of-way, speed limit enforcement, and highway lighting. Major planning by the Tennessee Department of Transportation (TDOT) in the 1980s and 1990s recommended median crossing closures, new overpass structures, and the widening into a six-lane facility.[2]

The construction of the Pellissippi Parkway from Oak Ridge to Alcoa required the construction of a cloverleaf interchange at US 129, which was completed in the late 1990s. Around the same time, the City of Knoxville installed lighting along the highway from the Little River north to the UTMC following annexation of the US 129 right-of-way and selected neighboring commercial and residential land-uses. Improvements were made to the US 129 interchange at I-40 and the "Buck" Karnes bridge was replaced with a new six-lane structure by the early 2000s. By 2000, TDOT began property acquisitions for the planned expansions of Alcoa Highway between I-40 and the Little River.[2]

In 2014, TDOT announced plans for improvements to the Alcoa Highway section of US 129 from I-40 to McGhee Tyson Airport in Blount County. The massive project, consisting of seven phases, called for the conversion of Alcoa Highway from a non-access-controlled highway into a full controlled-access highway (freeway). The overall project was given an initial cost of more than $233 million. The first phase of the project to begin was the Maloney Road to Woodson Drive phase in South Knoxville, with contract bidding opening in February 2016.[3] Construction work on the Maloney to Woodson phase of the Alcoa Highway improvement project began in June of the same year.[4] This section would be mostly complete by the fall of 2021, when new revisions for an access roadway to the Montlake Drive interchange were issued, expecting to be finished in the winter 2022.[5]

• Great Smoky Mountains National Park
• Interstate 3
• Little Tennessee River
• Tail of the Dragon
• Tennessee River

• Tennessee Department of Transportation (24 January 2003). "State Highway and Interstate List 2003".

• Media related to U.S. Route 129 in Tennessee at Wikimedia Commons
• Tennessee Department of Transportation