Those who rent cars in Italy should be aware of the danger of driving in any Italian cities. Most cities now have "traffic restriction" zones which you cannot enter without a special permit. Rental cars are not included. Very often, by the time you see the warning sign (presuming it is visible in the first place), it is TOO LATE to turn around. (Cynics might wonder if this is an accident). In any event, when you proceed, you are photographed and a ticket is automatically generated and forwarded to the company from which you rented the car. That company is required to provide the driver's name and address to the city, (in fact the rental companies are very happy to do so because they levy their own charges in the process). Then, sometime in the next year (in my case, it was nine months) you receive a direct notice from an Italian city demanding about 80 euros which must be paid within five days. The ONLY way to pay the fine is to arrange a telegraphic transfer of Euros to an Italian bank. This can be done at a cost of another $30 to $50 USD, depending on the fees at your local bank. If you do NOT pay the amount within five days, then the amount is increased by about 30 per cent (in my case, to 104 euros). If you do NOT pay the amount within 60 days, the amount is increased to 185 euros.
And, if you do not pay the fine, you can presume that the city will eventually direct the rental car company (which, remember, profits handsomely from this entire process), to charge it to your credit card along with whatever fees it deems reasonable.
In some cases, the city will not bother to communicate with you personally, but will bill the amount directly to the rental car company, which, in turn, will charge it to your credit card. (Don't bother cancel your credit card, as the bank will track you down and extract it from one account or another). It should be noted that the Italian national government wants to support its cities anyway it can, and so it has adopted a law giving the cities a full year in which to pursue offenders. Drivers should also be aware that the same method of fine collection applies to parking violations and to speed cameras (which are now operational throughout Europe, but are particularly common it Italy).
My advice: Next time, take the train.