More and more US travelers are reporting that their credit cards do no work when inserted into automated subway and/or train ticket machines in Italy, as well as other European countries. In Italy when they insert their credit card into the ticket machine when prompted, an error message pops up on the screen and a receipt with the message “Transazione Negata, data non valida” is issued.
A digital chip (EMV) embedded into a credit card is most likely needed to use a ticket kiosk in many cities in Europe. US based credit cards are slowing starting to introduce these chips in their credit cards.
Ask your credit card issuer about the EMV chip ( also know as chip and pin technology). Be prepared with cash to purchase tickets.