Before the construction of I-40, US 70 was the state’s primary east-west connection. Most of I-40 is parallel to US 70 a short distance away. US 70 was little upgraded outside the urban areas at the time due to the relatively small size of the cities and limited industrialization. Before the construction of I-40, almost everywhere this was a single-lane road that passed through every town.
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Construction history
Construction of I-40 was accelerated after the creation of the Interstate Highway system in 1956. I-40 was of great importance to Tennessee because it connected three of the four largest cities in the state. A large part of the rural routes between the major cities was opened in the 1960s. Some later openings were the sections around Memphis in 1980 and through Nashville in 1985. A short section in Knoxville predates the Interstate Highway system and opened to traffic in 1952. On August 2, 1973, the Hernando de Soto Bridge opened over the Mississippi River at Memphis.
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Opening history
Exit are sometimes also mileposts.
Memphis – Nashville
| From | Unpleasant | Length | Opening |
| exit 43 | Exit 52 | 13 km | 00-10-1963 |
| exit 35 | exit 43 | 13 km | 00-11-1963 |
| Exit 87 | Exit 95 | 13 km | 00-07-1964 |
| Exit 95 | Exit 108 | 21 km | 00-10-1964 |
| exit 28 | exit 35 | 12 km | 00-10-1964 |
| Exit 18 | exit 28 | 16 km | 00-11-1964 |
| exit 12 | Exit 18 | 10 km | 00-12-1964 |
| Exit 52 | Exit 87 | 56 km | 00-12-1965 |
| Exit 116 | Exit 163 | 76 km | 00-07-1966 |
| Exit 1 | Exit 4 | 5 km | 00-11-1971 |
| Exit 4 | exit 12 | 13 km | 00-03-1980 |
Nashville
| From | Unpleasant | Length | Opening |
| Exit 192 | Exit 196 | 6 km | 00-12-1962 |
| Exit 213 | Exit 216 | 5 km | 00-05-1963 |
| Exit 222 | Exit 232 | 16 km | 00-05-1965 |
| Exit 199 | Exit 205 | 10 km | 00-12-1966 |
| Exit 163 | Exit 182 | 31 km | 00-02-1966 |
| Exit 182 | Exit 192 | 16 km | 00-12-1966 |
| Exit 205 | Exit 207 | 3 km | 00-03-1971 |
| Exit 209 | Exit 210 | 2 km | 00-10-1972 |
| Exit 210 | Exit 213 | 5 km | 00-12-1985 |
Nashville – Knoxville
| From | Unpleasant | Length | Opening |
| Exit 387 | Exit 388 | 2 km | 00-12-1952 |
| Exit 357 | Exit 387 | 48 km | 00-12-1960 |
| Exit 258 | Exit 266 | 13 km | 00-12-1963 |
| Exit 267 | Exit 273 | 10 km | 00-12-1963 |
| Exit 232 | Exit 240 | 13 km | 00-08-1965 |
| Exit 240 | Exit 258 | 29 km | 00-12-1965 |
| Exit 273 | Exit 290 | 27 km | 00-12-1966 |
| Exit 318 | Exit 329 | 18 km | 00-07-1968 |
| Exit 290 | Exit 318 | 45 km | 00-04-1969 |
| Exit 347 | Exit 357 | 16 km | 00-06-1969 |
| Exit 329 | Exit 338 | 14 km | 00-07-1969 |
| Exit 338 | Exit 347 | 14 km | 00-08-1974 |
Knoxville-North Carolina state line
| From | Unpleasant | Length | Opening |
| Exit 416 | Exit 432 | 26 km | 00-09-1964 |
| Exit 432 | Exit 435 | 5 km | 00-12-1965 |
| Exit 435 | Exit 452 | 27 km | 00-10-1968 |
Later adjustments
Memphis
In Memphis, I-40 was originally planned to run directly from west to east through the city. The eastern part of this has also been constructed, but the route through the Overton Park district was ultimately not built, leaving a missing link of 4 kilometers. I-40 was eventually routed over the North Ring from Memphis. The eastern part is now called Sam Cooper Boulevard.
Because I-40 was routed over I-240, this caused problems at the interchange between I-40 and I-240 in eastern Memphis, which is designed for different traffic flows than is the case today. A new flyover for traffic from Nashville to I-240 south was built in 2004, and a flyover for traffic from Arkansas to Nashville was constructed in 2014-2015, this was the first 4-level interchange in Memphis. The flyover opened on September 8, 2015 so that I-40 has two lanes of through traffic here. In 2015, the left lane was converted into a HOV lane in the eastern suburbs of Memphis over a distance of 10 kilometers.
Nashville
In 2004-2005, I-40 in western Nashville was widened from 2×3 to 2×4 lanes between Briley Parkway and I-440.
I-40 has had greater capacity east of Nashville for some time. The section between SR-155 and Mount Juliet has had 2×4 lanes since the early 1990s. In 2003-2006, I-40 was widened to 2×5 lanes in eastern Nashville, between I-24 and SR-255. In 2013-2014, I-40 was widened further from Mount Juliet to SR-109 to 2×3 lanes.
Knoxville
I-40 at Downtown Knoxville.
I-40 runs west from Knoxville along with I-75. This section originally had 2×3 lanes and was widened to 2×4 to 2×5 lanes in circa 2006 between I-140 and I-640 between Farragut and Knoxville.
Circa 2007, a short section of I-40 near Downtown Knoxville was widened from 2×2 to 2×4 lanes on overpasses. I-40 on the east side of Knoxville has also been widened with a parallel structure. In 2008, a large-scale reconstruction of Interstate 40 in Knoxville began. The road was completely closed here until the end of 2009. On June 12, 2009, the road was reopened, ahead of schedule.
Traffic intensities
Every day, 37,000 vehicles cross the Mississippi River at Memphis, rising to 71,000 vehicles at the interchange with I-69. After that, up to 122,000 vehicles will travel on the north-south section, which is double-numbered with I-69, and 90,000 vehicles on the North Ring of Memphis. East of I-240 is the busiest point at 153,000 vehicles per day, falling eastward to 54,000 vehicles west of I-269 and 32,000 vehicles east of it. As far as Jackson 35,000 vehicles, peaking at 55,000 vehicles through Jackson, then dropping back to 30,000 to 35,000 vehicles over a long stretch to Dickson, near Nashville.
West of I-840 at Dickson, there are 47,000 vehicles per day, then temporarily dropping to 38,000 vehicles, then rising closer to Nashville after each connection, to 100,000 vehicles west of TN-155 and 127,000 vehicles between TN-155 and I -440. After that, 100,000 vehicles drive between I-440 and I-65 and 105,000 to 132,000 vehicles on the double-numbered I-65 along the west side of downtown Nashville. The portion on the south side of downtown between I-65 and I-24 has 128,000 vehicles per day, peaking at 189,000 vehicles on the double-numbered I-24 southeast of downtown. After I-24 turns off, this drops to 143,000 vehicles, then drops to 60,000 vehicles west of Lebanon after each junction. East of I-840, there are 75,000 vehicles per day.
East of Lebanon, traffic volumes drop to 30,000 to 40,000 vehicles on the long stretch to I-75 west of Knoxville. Between I-75 and I-140 there are 90,000 to 131,000 vehicles per day, peaking at 194,000 vehicles west of the interchange with I-75 in Knoxville, the busiest section of I-40 in Tennessee. 154,000 vehicles drive through downtown Knoxville, dropping to 95,000 vehicles east of downtown and 102,000 vehicles east of I-640. The intensities then remain quite high with 70,000 vehicles until the junction with I-81. The last section through the Great Smoky Mountains to the North Carolina border is the quietest section of I-40 at 20,000 vehicles per day.
Lane Configuration
| From | Unpleasant | Lanes | Comments |
| exit 0 | Exit 3 | 2×3 | Memphis |
| Exit 3 | Exit 5 | 2×4 | Memphis |
| Exit 5 | exit 12 | 2×3 | Memphis |
| exit 12 | exit 13 | 4+6 | Memphis |
| exit 13 | Exit 18 | 2×4 | Memphis |
| Exit 18 | Exit 196 | 2×2 | |
| Exit 196 | Exit 211 | 2×3 | Nashville |
| Exit 211 | Exit 213 | 2×4 | Nashville |
| Exit 213 | Exit 215 | 2×3 | Nashville |
| Exit 215 | Exit 226 | 2×4 | Nashville |
| Exit 226 | Exit 368 | 2×2 | |
| Exit 368 | Exit 376 | 2×3 | |
| Exit 376 | Exit 379 | 2×4 | |
| Exit 379 | Exit 385 | 2×3 | Knoxville |
| Exit 385 | Exit 386 | 2×4 | Knoxville |
| Exit 386 | Exit 421 | 2×3 | |
| Exit 421 | Exit 451 | 2×2 |
