I'm wondering if I buy a Eurail Continuous Global pass but don't mind traveling on slow trains and transferring a lot, I can avoid paying any fees or making any advance registrations...i.e. just "hop on".
I've read that although almost all high-speed and otherwise desirable train services offered by a Eurail pass require an additional fee for seat reservations, but that all regional short-distance trains don't require additional fees.
Here's a Eurail map: http://www.eurail.com/sites/eurail.com/files/documents/eurail_railway_map_2014.pdf Are the RED lines possible to travel using a Eurail pass without additional fees or tickets?
What else might there be additional fees or advance reservation requirements for? Traveling at certain times of day? Traveling high-traffic commuter routes during rush hour?