US 45 Bypass begins at an intersection with US 45 and US 70 in downtown. It goes as a 4-lane divided controlled-access expressway, concurrent with US 70/SR 1, to leave downtown and pass through industrial areas to have a signalized intersection with State Street. It then curves to the north and US 70/SR 1 immediately split off and go east along Airways Boulevard towards McKellar-Sipes Regional Airport. US 45 Bypass continues through suburban neighborhoods to pass through a business district before having an interchange with Hollywood Drive. It then has a signalized intersection with US 412 Bus before widening to a 6-lane at-grade boulevard. It then passes through another business district before having a cloverleaf interchange with I-40/US 412. US 45 Bypass becomes an expressway once again and immediately has an interchange with Vann Drive and Country Club Lane. It passes Union University before having at-grade intersections with Union University Drive/Channing Way, Oil Well Road, Old Humboldt Road, and Ashport Road, while maintaining controlled access otherwise through the area. US 45 Bypass then comes to an end at an interchange with US 45 and Passmore Lane, with unsigned SR 186 continuing north along US 45/SR 5.
SR 186 begins as a 2-lane secondary highway in Gibson County in Trenton at an intersection with US 45W slightly southeast of downtown and is known as Gibson Highway. It goes southeast through farmland to have an intersection with SR 420 to enter the town of Gibson, where it passes through downtown and has an intersection with US 79/US 70A/SR 76.. From here, SR 186 continues south through farmland to have a short concurrency with SR 187 and have an intersection with SR 152 before crossing into Madison County.
Madison County
SR 186 south through farmland to enter Three Way and has an intersection and becomes concurrent with US 45E/SR 43, where it becomes a 4-land divided highway, as well as it becomes an unsigned primary highway. They go southwest and almost immediately come to an interchange with US 45W/SR 5, where SR 43 ends and US 45E and US 45W merge to become US 45, which SR 5 and SR 186 follow south. They continue south for about before coming to an interchange with Highland Street, where US 45/SR 5 branch off and SR 186 follows US 45 Bypass. US 45 Bypass/ SR 186 continue south around the western side of the city of Jackson through suburban areas as a 4 to 6 lane expressway, where it has interchanges with Vann Drive, I-40/US 412, an at-grade intersection with US 412 Bus/SR 20, and an interchange with Hollywood Drive. US 45 Bypass/SR 186 then come to an intersection and become concurrent with US 70/SR 1, where it makes a sudden sharp turn to the east to enter downtown, where it becomes an at-grade surface route before US 45 Bypass and SR 186 both come to an end at an intersection with US 45/SR 5. The portion of SR 186 from Three Way to Downtown Jackson is unsigned.
Future
The city of Jackson along with TDOT is planning on re-routing SR 186 away from downtown. Under the current plans, it would extend the bypass south across the South Fork of the Forked Deer River and connect it with US 45 in South Jackson. It would route through traffic away from the central business district and give another crossing for South Jackson commuters.
