We noticed that some people had very wide rolling suitcases that could not be rolled in the aisles or corridors. If you are using a rolling case, make sure that it is fairly narrow.

Sorry, I can't find the figure - but I found this statement: The width of an open central corridor in European 2nd class cars is around 495 mm (19.5 inches) in Google Groups. You might also try http://www.seat61.com/

BTW, we found train travel in Italy fine and inexpensive.

Frances Toronto, Canada