A busy interstate is back open in Tennessee, at least going one direction.I-75 was closed in late February after a rockslide south of the TN/KY state line.Crews have been working to clear the slide, which blocked the northbound lanes. Southbound lanes were closed to stabilize rocks that could have fallen into the lanes.The Kentucky Department of Transportation reported Thursday that southbound lanes are open again.Northbound lanes remain closed, but at least one lane is expected to reopen by March 24.