If you have made train reservations ahead of time and already have your tickets but miss a train, are they good for the next train to your destination?
Our train engine broke down and we missed a reserved connection. We landed up hoping on and off rural trains to get from CT to Venice. We had our tickets for our original trains and no one checked our tickets on any of the trains we were on. We did put them in the machine for stamping and dating at the beginning of our "adventure".
Your tickets are good but you need to go to the ticket window and make a new seat reservation.
If you have Eurostar tickets, like Doug says you have to go to a ticket window and get new seat assignments. If you have tickets on A regionale or Intercity train with open seating... just catch the next train!
We've missed a couple and those tickets are good for that "destinantion and/or route" -- technically until you "validate" (stamp) them in the yellow machines. We've just gotten into the habit of NOT STAMPING until we're walking up to and ONTO the train!
Ciao,
Ron