I thought I was in a NASCAR race for the time I was on I-81. Fortunately, I was driving a van and not our coach. I have never been on such a crowed interstate. The truck traffic was horrific, the car traffic was bad & it was practically bumper to bumper at 70mph and faster. The northbound traffic was just as bad.
I got on at Mt. Jackson (SB) and got off a few miles down the road and took Hwy 11 south to Lexington, VA. Hwy 11 is a good road and was much less stressful than 81. Just pay attention and avoid taking the "bus route" and wind up downtown.