Why not take the train all the way to DC, and then cycle back to Pitts. The cycling in DC is much nicer, many more paths & routes. Besides, if you didn't want to cycle up the Cumberland Gap, you can take the train to Frostburg, which eliminates most of the climbing. Then once at the top, who have many miles of gentle downhill riding. You could likely get a taxi or shuttle from Boston into Pitts. If you didn't want to ride into the city.