Interstate 75 in Tennessee

Scenic view along Interstate 75 southbound crossing White Oak Mountain

Interstate 75 enters Tennessee on the eastern side of East Ridge, a southern suburb of Chattanooga. Less than ¹⁄₂ mile (0.80 km) mile into Tennessee is an interchange with U.S. Route 41 (US 41/Unsigned US 76). About a mile later, at exit 2, is a three way interchange with the eastern terminus of Interstate 24, which runs west into Downtown Chattanooga and to Nashville. At this interchange, I-75 turns northeast, running along the eastern boundary of Chattanooga. Almost two miles later is an interchange with State Route 320 (SR 320), which connects to East Brainerd, and about a half mile later is a three way interchange with the southern terminus of SR 153, a controlled access highway that runs northwest to the Chattanooga Metropolitan Airport and crosses the Tennessee River on the Chickamauga Dam. Accessible from the northbound lanes at this interchange is Hamilton Place Boulevard, a connector to Hamilton Place Mall. The southbound lanes of I-75 are also accessible from an entrance ramp from this road. At this point, I-75 enters a large commercial area dominated by Hamilton Place, and has an interchange with Shallowford Road about a mile later. A few miles later, at exit 7, I-75 has an interchange with US 11 southbound, US 64 westbound and SR 317 westbound, and begins a concurrency with these respective routes. Turning slightly northeast, the interstate crosses a Norfolk Southern Railway and at exit 9, SR 317 splits off to the east. I-75 then crosses a steep ridge, passing between the Enterprise South Industrial Park to the west and Collegedale to the east. A few miles later, in Ooltewah, US 11/64 split off at exit 11, where the route narrows to six lanes. I-75 then turns northwest, and narrows to four lanes.

I-75 northbound in Athens.

A few miles later, I-75 begins a steep ascent up the western slope of White Oak Mountain, where the northbound lanes receive a truck climbing lane. At this point, the interstate turns northeast, and for the next three miles traverses east northeast over the top of White Oak Mountain, where it crosses into Bradley County. I-75 then runs for the next several miles through a predominantly wooded and agricultural area and crossing a few ridges before reaching Cleveland at an interchange with APD-40 eastbound (US 64 Bypass), a bypass and connector to US 64. Running along the western edge of Cleveland, I-75 has an interchange with SR 60 about 4.5 miles later, also crossing Candies Creek Ridge at this location, and less than 2 miles later, an interchange with Paul Huff Parkway, a major thoroughfare along the northern part of Cleveland. The interstate then leaves Cleveland, and enters rural northern Bradley County, running northeast. Beginning at this point and continuing for nearly 60 miles, I-75 is very straight and flat, with few curves. Nearly the entirety of this section also contains an extremely wide median, mostly separated by trees. In some locations, the north and southbound lanes are as much as a half mile apart.

About twelve miles north of the central business district of Cleveland, I-75 curves to the northeast, and crosses the Hiwassee River into McMinn County, and then curves back to the northwest. This area is extremely susceptible to fog hazards, which obscures the visibility of drivers, and several bad accidents have occurred on this section as a result. Running through mostly wooded and agricultural areas, I-75 reaches Athens about 15 miles later, and has an interchange with SR 30, a major east-west corridor in East Tennessee. Running through northern McMinn County, the interstate passes near several unincorporated communities, and has interchanges with several secondary state highways. Around mile marker 58, I-75 enters Monroe County, and a few miles later passes near the town of Sweetwater, containing an interchange with SR 68, another major primary state highway. A few miles later, I-75 crosses into Loudon County. At exit 72 is an interchange with SR 72, which connects to Loudon, and a few miles later, the highway crosses the Tennessee River on the Mitchell W. Stout Memorial Bridges. I-75 then enters a predominantly commercial and residential area, and has an interchange with US 321 and SR 95 in Lenoir City. These routes also connect to Oak Ridge and Maryville. Curving slightly to the west and then again to the east, I-75 reaches an interchange with I-40 westbound about three miles later, where it begins a concurrency with I-40. About 20 miles west southwest of Knoxville, the concurrent routes widen to six lanes and cross into Knox County less than a mile later.

I-75 north, along its concurrency with I-40 east in Knoxville

Running approximately east northeast the two interstates pass through the western suburbs of Knoxville including Farragut and West Knoxville. Along this concurrency exits are numbered according to I-40 mileage. At exit 374 is an interchange with SR 131 (Lovell Road), where the highway widens to eight lanes, and less than two miles later is a four way interchange with the Pellissippi Parkway (SR 162 westbound, I-140 eastbound), which connects to Oak Ridge to the west and Maryville to the east. At exit 380 is an interchange with US 11/70 (Kingston Pike), which connects to the West Hills neighborhood and West Town Mall. This section is the most heavily traveled section of highway in Tennessee, with an annual average daily traffic (AADT) volume of more than 210,000 vehicles. About 5 miles (8.0 km) later, at an interchange with the western terminus of I-640, the northern bypass around downtown Knoxville, I-75 splits north off of I-40 and onto a concurrency with I-640. Along this concurrency, exits are numbered according to I-640 mileage. Heading north, the interstates come to an interchange with SR 62 (Western Avenue) about a mile later. About 1.5 miles later is a complicated interchange with I-275 southbound, the former route of I-75, and US 25W, where I-75 splits off.[2]

Leaving Knoxville, I-75 turns north, crossing several paralleling ridges of the Ridge and Valley Appalachians. The terrain for the next 20 miles (32 km) of I-75 north of Knoxville are mostly flat. At exit 112 in Powell, I-75 once again has an interchange with SR 131, and the Interstate narrows from six to four lanes. Entering a rural area, I-75 runs along a creek valley for the next several miles that bisects several ridges in a crooked and hazardous segment marked by several S-curves. Maintaining its north-northwesterly direction, I-75 crosses into Anderson County. Beyond this section, the Cumberland Mountains become visible in the distance. At exit 122 the Interstate has an interchange with SR 61 near Clinton. I-75 then descends sharply into a valley, crossing the Clinch River a few miles later. About four miles (6.4 km) later, near the community of Rocky Top, I-75 has interchanges with US 441, and US 25W, running concurrently with the latter. The Interstate then crosses into Campbell County.

View from I-75 on top of Jellico Mountain near the Kentucky border.

For approximately the last 30 miles (48 km) in Tennessee, I-75 traverses the Cumberland Mountains. This entire section is considered very scenic and is prone to rockslides in many locations. Around milepost 130, I-75 begins its first major ascent for a few miles before leveling out on one of the plateaus of Cumberland Mountains, and at exit 134, near the community of Caryville, US 25W splits off and I-75 begins a concurrency with SR 63. The Interstate then begins another ascent, adding a truck climbing lane going northbound. About six miles (9.7 km) later, the highway levels out on another one of the plateaus and the truck lane terminates. Less than a mile later, SR 63 splits off near the unincorporated community of Pioneer. Traveling through a further sparsely populated rural area marked by dense woodlands, I-75 remains relatively flat for the next few miles before beginning another ascent up the Cumberland Mountains, once again adding a truck climbing lane. Jellico Mountain is a sub-mountain range of the Cumberland Mountains that the interstate traverses near Jellico. I-75 curves sharply to the northeast and about a mile later, it reaches the crests of Jellico Mountain where the truck lane ends. The interstate then climbs the crests of Jellico Mountain for about another four miles (6.4 km) before levelling out on top of Jellico Mountain at an elevation of about 2,000 feet (610 m) and has an interchange with US 25W in the city of Jellico. Less than a mile later, I-75 enters the hilly terrains of eastern Kentucky.

Construction of I-75 in Tennessee began in 1958 with short segments in Chattanooga and Knoxville. The concurrent segment with I-40 between the split near Lenoir City and downtown Knoxville opened to traffic on December 2, 1961.[3] The route was completed through Chattanooga on July 17, 1963, with the completion of the 6.6 miles (10.6 km) segment between the split with I-24 and US 11/64 (Bonny Oaks Drive).[4] I-75 was completed through Knoxville in late 1965.[5] The section between Ooltewah and SR 60 in Cleveland opened on October 18, 1966.[6] Like much of the interstate system in rural Tennessee, priority was generally given to completing rural segments in Middle and West Tennessee over East Tennessee, but the last approximately 35 miles (56 km) segment of I-75 in Tennessee, located mostly in Campbell County, was constructed much earlier than most of the rural segments in Tennessee, reportedly due to the influence of then-Congressman and later U.S. Senator Howard Baker Jr., who was from that area.[7] By 1963, the 1 mile (1.6 km) section between US 25W in Jellico and the Kentucky state line was open to traffic.[8] The 6.8 mile segment between US 25W in Caryville and US 441 in Anderson County was completed in October 1964. Portions of this segment predated the interstate system.

The 25.8 miles (41.5 km) section between US 25W/SR 63 in Caryville and US 25W in Jellico was opened to traffic on October 22, 1968.[9] The section between SR 60 and SR 308 in Bradley County began construction in 1968, but was stalled shortly thereafter.[10] Construction resumed in 1972, and the segment was opened to traffic on January 23, 1973.[11] The section between US 25W north of Knoxville and SR 61 in Clinton broke ground in segments, beginning in August 1968,[12] and was opened to traffic on August 1, 1972.[13] The approximately 6 miles (9.7 km) segment between SR 61 and US 441 in Anderson County was completed in September 1973.[14] The section of the highway between SR 308 near Charleston and SR 30 in Athens opened on December 24, 1973, and was completed the following spring.[15] The last section of I-75 in Tennessee, approximately 32 miles (51 km) between SR 30 in Athens and US 321/SR 95 in Lenoir City, was opened to traffic on December 20, 1974, in a ceremony officiated by then-governor Winfield Dunn.[16] The last section of I-40 and I-81 in Tennessee was opened on this same day.[17]

I-75 originally continued into downtown Knoxville then turned to the north at Malfunction Junction, following what is now signed as I-275. When the western section of I-640 was completed in 1982, I-75 was moved to overlap the auxiliary route to divert through traffic away from downtown in preparation for the 1982 World's Fair. This concurrency is somewhat unusual in that the exit numbers and mile markers follow the auxiliary route I-640 instead of I-75 mileage.

An approximately five mile section of I-75 in northern Bradley and southern McMinn Counties, including the bridge over the Hiwassee River is prone to hazards from dense fog in the morning, which can severely obscure the visibility of drivers. This segment is located near several heavy industries including the Resolute Forest Products paper mill, formerly Bowater, which operates settling ponds along the interstate. This segment has been the site of several serious multivehicle accidents, the first of which occurred on March 9, 1974, less than three months after the section opened to traffic, and before it had been declared complete.[18] This accident involved 18 vehicles, and killed three and injured 10.[18] A total of six multivehicle accidents occurred along this stretch in the 1970s.[18] The worst, which took place on November 5, 1978, involved 62 vehicles and injured 46, and took place on the Hiwassee River Bridge.[19] After a multivehicle accident on April 15, 1979 which involved 18 vehicles, killed three, and injured 14, TDOT identified the stretch as prone to fog hazards, and agreed to install warning signs with flashing warning lights, which would activate if fog was detected. After this, no serious fog related accidents occurred for more than 11 years.

On December 11, 1990, a 99 vehicle accident occurred in this same area that resulted in 12 deaths and 56 injuries.[20] This accident was considered unusual, due to the density and sudden appearance of the fog, and initial speculation arose about the possibility of the role of water vapor.[21] Extensive investigations followed, and some meteorological experts believe that the fog may have been caused by an unusual phenomenon known as a temperature inversion.[21] Several lawsuits were filed against Bowater, alleging that they had contributed to the fog with their water vapor emissions.[21] A study conducted by researchers at the University of Tennessee in January 1979 had concluded that Bowater's settling ponds were possible contributors to fog in the area.[21] Several lawsuits were also filed against the state of Tennessee, which claimed that TDOT had failed to install adequate warning systems along this stretch of I-75, a position that Bowater also took.[18] The existing fog warning lights were reportedly not working on this day.[22] After settling with the family members of accident victims and survivors in court, TDOT instituted several safety measures along this stretch of highway, including re-striping the roadway with extra markings to make it more visible and installing a computerized fog detection system, which contains a warning system with flashing lights, electronic signs, variable speed limits, and electronic controlled swing gates which block access to the interstate from six entrance ramps in and near this stretch in the event of dense fog.[18] Between mileposts 31 and 39, the highway is designated as a fog advisory zone.[23] A $5.5 million upgrade was completed to this system in 1993, and in 2006, a $6.6 million upgrade was completed which installed video cameras.[18] Bowater also agreed to limit the use of their settling pond closest to the interstate.[18] The accident was profiled in a 1997 episode of the show Forensic Files.[22]

The entire section of I-75 in Tennessee north of Knoxville has been subject to many geological difficulties, particularly the last 30 miles through the Cumberland Mountains.

In March 2005, the southbound lanes of Interstate 75 were shut down between mile marker 141 to 143 due to a rockslide below the roadway that caused the pavement to partially collapse.[24]

In March 2012, the southbound lanes of the interstate were again closed to traffic between mile markers 141 and 143 in Campbell County, Tennessee due to a slide beneath the roadway.[25] This was later followed by a second slide in early May 2012[26] that caused a portion of the southbound lanes to completely erode and forced the detour lanes to be closed.

In February 2016, a rock slide closed I-75 near Caryville, Tennessee.[27]

On March 28, 1994, a runaway barge that had broken loose from its mooring due to flooding struck the I-75 bridge over the Tennessee River, along with the US 11 bridge and a railroad bridge. The collision broke loose a chunk of concrete from a post, but engineers determined that it caused no major structural damage. I-75 had been closed to traffic on this section in preparation for the collision.[28]

On April 1, 2019, part of the bridge on I-75 southbound over the ramp from I-24 westbound to I-75 northbound at the split in Chattanooga collapsed, injuring one person and blocking traffic for hours.[29][30][31] The bridge, built in 1959, is one of the oldest on I-75 in Tennessee, and the interchange is the site of frequent accidents. TDOT's chief engineer said that the collapse was most likely caused by weakening of the bridge's rail that occurred when an illegally oversized load hit the bridge.[32]

Throughout its history I-75 has seen many reconstruction and widening projects in Tennessee.

The first major reconstruction project was a widening of the concurrent segment of I-75 and I-40 from four to six lanes between the interchange near Lenoir City and Downtown Knoxville, which began in the late 1970s.[33] In the latter 1980s, I-75/I-40 was widened from six to eight lanes between the Pellissippi Parkway and Papermill Road, and multiple interchanges along this segment were reconstructed.[34] These segments have since seen more improvements.

I-75 was widened from four to six and eight lanes in Chattanooga between the interchange with I-24 and SR 153 in the late 1980s. Between 1998 and 2010 a series of projects reconstructed and widened I-75 between SR 153 and north of US 11/64 in Ooltewah. The first of these projects, which began in late 1998 and was completed in 2001, rebuilt the interchange with SR 153, changing the approach of two flyover ramps that connect to I-75 northbound from the left to the right side of the road. This project also modified the interchange with SR 320, removing two cloverleaf loop ramps from I-75 southbound, and moving the access to the entrance ramp from I-75 southbound to a point near the interchange with SR 153. The next project, which widened I-75 further between mileposts 6 and 9 and improved the interchange with SR 317, was completed in November 2005.[35] A new interchange was constructed in 2006 to provide access to the Enterprise South Industrial Park, which at that time was in the process of redevelopment.[36] This interchange, which became exit 9, now provides access to the Volkswagen Chattanooga Assembly Plant, and was not opened until 2010. A segment of SR 317 was later routed onto a concurrency of I-75 between exit 11 and this interchange. Exit 9 was designated as the Bredesen-Ramsey Interchange in 2015 in honor of the efforts of then-governor Phil Bredesen and county mayor Claude Ramsey to bring Volkswagen to Chattanooga.[37] The last of these projects, which began on November 8, 2007, widened I-75 from approximately milepost 10 to milepost 13, just north of the interchange of US 11/64, and included reconstruction of this interchange, including the addition of a loop ramp, and improvements on this road.[38] This project was completed on August 12, 2010, four months ahead of schedule.[39][40]

On May 1, 2008 I-75 northbound traffic was re-routed back along its original path in downtown Knoxville along Interstate 275 as part of SmartFix 40, a major construction project that includes closing a portion of I-40. Traffic was re-routed along I-275 as the ramp from I-640 eastbound/I-75 northbound to I-75 northbound is only one lane which causes traffic delays at peak times.

In December 2018 a contract was awarded to rebuild the interchange with I-24 in Chattanooga.[41] Preliminary work began in May 2019, with completion estimated by June 2021.[42]