I wonder how much traffic could be replaced by extending train service down the length of I-81 to Bristol. Even 10% would be huge.
Bump
Less than you are thinking, much of the truck traffic is trucks avoiding the highly congested 95 corridor and my understanding is that the class 1 railroads are not very interested in intermodal traffic that travels less than ~500 to 750mi or about one day's haul as they cannot move it any faster.