At least 15 special routes of U.S. Route 78 have existed and at least seven have been deleted.
Mississippi
Red Banks business loop
Hickory Flat business loop
Alabama
Hamilton–Graysville alternate route
Carbon Hill–Jasper alternate route
Birmingham–Irondale alternate route
Birmingham truck route
Leeds truck route
Anniston business loop
Alabama–Georgia
US 78N
U.S. Route 78N (US 78N) was a northern divided U.S. highway that comprised the current mainline of US 78 from Heflin, Alabama, to Villa Rica, Georgia.
The road that would eventually become US 78N was established in 1920, as SR 8 from the Alabama state line to Villa Rica. By the end of the third quarter of 1926, US 78 was established, being designated along a local roadway from Heflin to the state line, and SR 8 from the state line to Villa Rica. The next year, US 78 split into two divided routes, with US 78N being designated from Heflin to Villa Rica, on the northern segment of SR 8 (thereby replacing the mainline highway). In 1928, Alabama State Route 4 (SR-4) was designated along US-78N. By May 1933, US 78N/SR 8 were paved from Bremen to Villa Rica. Later that month, US 78N/SR 8 were paved from east of the Alabama state line to Bremen. The next month, US 78N/SR 8 were paved west to the Alabama state line. By November 1934, US 78N was redesignated as part of mainline US 78.
US 78S
U.S. Route 78S (US 78S) was a southern divided U.S. highway that comprised the current length of Alabama State Route 46 from Heflin, Alabama, to the Georgia state line, SR 166 from the state line to Carrollton, and SR 61 from Carrollton to Villa Rica.
The road that would eventually become US 78 was established in 1920 as part of SR 34 from Carrollton to Villa Rica. By the end of the third quarter of 1921, SR 16 was designated from the Alabama state line, west of Bowdon to Carrollton. By late 1926, SR 16 and SR 34 were redesignated as a southern branch of SR 8. In 1927, US 78 split into two divided routes, with US 78S being designated from Heflin to Villa Rica, via Bowdon and Carrollton, on the southern branch of SR 8. In 1928, Alabama State Route 4 (SR-4) was designated along US-78N, while SR-46 was designated along US-78S. By 1932, US 78S/SR 8 were paved from Carrollton to just southwest of Villa Rica. By the end of 1934, US 78S/SR 8 were paved from the Alabama state line to a point near Bowdon. By November 1934, US 78S was redesignated as US 78 Alternate. By the beginning of 1948, the southern branch of SR 8 was redesignated as SR 8 Alternate. By the middle of 1954, SR 8 Alternate was redesignated as SR 166 from the Alabama state line to northeast of Carrollton) and SR 61 from there to Villa Rica.
Heflin–Villa Rica alternate route
U.S. Route 78 Alternate (US 78 Alt.) was an alternate route of US 78 in northeast Alabama and northwest Georgia. It comprised the current length of Alabama State Route 46 (SR 46) from Heflin, Alabama, to the Georgia state line, SR 166 from the state line to Carrollton, and SR 61 from Carrollton to Villa Rica.
The road that would eventually become US 78 Alternate was established in 1920 as part of SR 34 from Carrollton to Villa Rica. By the end of the third quarter of 1921, SR 16 was designated from the Alabama state line, west of Bowdon to Carrollton. By late 1926, SR 16 and SR 34 were redesignated as a southern branch of SR 8. In 1927, US 78 split into two divided routes, with US 78S being designated from Heflin to Villa Rica, via Bowdon and Carrollton, on the southern branch of SR 8. In 1928, SR 4 was designated along US-78N, while SR 46 was designated along US-78S. By 1932, US 78S/SR 8 were paved from Carrollton to just southwest of Villa Rica. By the end of 1934, US 78S/SR 8 were paved from the Alabama state line to a point near Bowdon. By November 1934, US 78S was redesignated as US 78 Alt. By the beginning of 1948, the southern branch of SR 8 was redesignated as SR 8 Alternate. By the beginning of 1953, US 78 Alt. was decommissioned. SR 8 Alternate became SR 166 from the Alabama state line to northeast of Carrollton by the middle of 1954, and SR 61 from there to Villa Rica.
Georgia
Athens business loop
U.S. Route 78 Business (US 78 Bus.) in the Athens – Clarke County metropolitan area is a Bannered U.S. Highway that is concurrent with Georgia State Route 10 (SR 10) for its entire length. Its western terminus is at an interchange with US 29/SR 8/SR 316 and US 78/SR 10, southeast of Bogart in Oconee County. Its eastern terminus is at US 29/US 78/US 129/US 441/SR 8/SR 10 Loop/SR 15. The roadway continues as US 78/SR 10.