Originally Posted by
pacificcyclist
It's carry on. Regular bike is treated as checked baggage either boxed or stored on the bike rack. Depending on which Amtrak you take, the most they can take on the rack is 6 bikes (Amtrak Cascade, Piedmont and Downeasters) whereas Surfliners take 3. But unlike the airline, the carryon folded bike goes on the baggage rack.
I am envious and inspired by your setup. I am going to do a bit of bike/train touring this summer and your setup is perfect!