I traveled up and down the East Coast with my dad when he was in a wheelchair. Every city was a little different but Amtrak has made their trains this way. A special ramp is needed, which has to be fetched by someone. Baltimore was the worst about it, but they did get us on just fine, and kicked a guy out of the handicapped starting. New York City was incredible. Dude hung out with us until our train showed up and made sure we got on and situated before regular boarding started. Though I think he had dealt with something similar personal and took it upon himself. DC was at about the level you'd expect and was pretty pleasant.