Why would you take I-81 from Boston to dc? Just curious.
To Avoid the Cross-Bronx Expressway, for one reason. I-95 sucks in all of it’s incarnations, except perhaps for the 100 mile stretch between DC and Richmond. (LOTS of “Diversions” on that road...Manasses, Fredericksberg, Chancellorsville, Spotsylvania, etc.)
Also, I liked to peel off at RT55 and cruise the mountains of West Virginia for a nice diversion.
I-81 is better than I-95 despite the trucks. Truck drivers are generally safe and predictable (with a few exceptions). In contrast I-95 is full of druggies and idiots driving 90 mph. I-95 has cities full of bad drivers along its route.
Probably takes I-84 thru CT & NY to Scranton, then down I-81 to Harrisburg, I-83 to Baltimore, and I-95 to white-hut town.
Always drive that route from here in MD to avoid the "real" traffic on the east-coast route...Well worth the extra hour of driving...Usually relaxing...