State Route 166 Improvements

Lewis and Maury Counties


The project for State Route 166, between State Route 6 (US 43) in Maury County and State Route 99 (US 412) in Lewis County, includes reconstruction and widening  for approximately 6.5 miles. Design plans also include construction of a new interchange at SR 6.

Purpose and Need

SR 166 is considered a rural major collector route. It connects to SR 99, providing a route between Mt. Pleasant in Maury County and the Natchez Trace Parkway and Hohenwald in Lewis County. An Advanced Planning Report (APR) was approved in 1998 to relocate and widen SR 166, as well as widen SR 99. Currently, widening projects in Lewis County are nearing completion. When all planned improvements are finished, the new facility will provide improved safety, capacity, and mobility along the corridor for existing and future traffic.


Due to the complexity of the project, improvements to SR 166 have been divided into two smaller sections or phases.

  • Interchange at SR 6 (US 43) in Mt. Pleasant

Construction is currently underway to separate the intersection of SR 166 and SR 6 by creating a diamond interchange. This separation calls for a new bridge on SR 166, which will create an overpass over SR 6. SR 166 will be widened to three lanes through the interchange area, from approximately 1,200 feet east of SR 6 to 500 feet west of SR 6, where SR 166 will then tie-in to the existing two-lane roadway.

  • from SR 6 (US 43) in Mt. Pleasant to SR 99 (US 412) at the Lewis County Line

To the west of the new interchange, SR 166 will be widened from a three-lane undivided roadway to a four-lane divided roadway with two 12-foot travel lanes in each direction and a 48-foot grass median. The right-of-way width will be a minimum of 250 feet throughout the project. SR 166 will connect with SR 99 near Ridgetop Road in Lewis County.