Multiple vehicles were involved in a crash at Mile Marker 24 in Bradley County just before 3 p.m.
Five people were reported injured.
The crash, in drizzly weather, had traffic backed up for miles.
It was not expected to be cleared until around 6 p.m.
As traffic stalled, there was also a crash just north of there at Mile Marker 27 near Paul Huff Parkway at 3:55 p.m.
Some of those stuck in traffic were on the way to participate in the Ironman Triathalon in Chattanooga over the weekend.
One man from Boone, N.C., said his son was concerned that he was not going to make it to check-in by the 6 p.m. deadline.