I know this is a old thread but recently I tried to get answers about bringing trikes. I posted this in the Gold Wing section by accident.
I spoke with 3 people. 2 said yes certain trikes but could not tell me which ones or and sizes. The third said no trikes.
We were looking at doing the Auto train the week after Memorial Day, hit Gettysburg then up into the Adirondacks and back down to for a train ride back home but now we're are headed to NOLA, Memphis and who knows on our first long road trip with the trike.
I have taken my bike on the AT a couple times. Worked out great.