Smog and No Traffic Zones
Smog has become a major problem in practically all major Italian cities. If you are looking down from the hillsides (for example in Turin - but also in other cities) - you see a greyish covering which gives you an indication of how bad air pollution has gotten - or if you like, you can see it from a satellite. Besides ruining the beautiful monuments and buildings, it can seriously affect people's health. Even back in 2002, the World Health Organization published a study on the effects on health of air pollution in Italy: See Report. And more recently, it has begun to affect people's driving and commuting habits!
Already in February of this year, several Italian cities have exceeded the permissible number of days per year that the concentration of microparticles in the air exceeds maximum safe levels - so they are having to do something about it. And that something is blocking traffic in the cities.
Initially they started doing it on Sundays - but then they realized that traffic on Sundays was pretty limited, and blocking traffic on that day was not enough. So they started adding additional days within the week. There is still a lot of discussion about whether the traffic blockage is gong to help, but at least for now, that seems to be the solution that will be pursued.
When traffic is blocked, and which types of vehicles are blocked, changes from week to week, and may be cancelled if there is a strong wind that blows away the pollution. Generally the authorities also use alternating odd-even license plates (dispari-pari) so that not everyone is affected. Which means that if you are lucky and you and your spouse have corresponding odd-even license plates, you can trade cars to go into town with the "alternative" car. I could imagine that there would be a market for "2nd" license plates for cars - but this would be totally illegal!
If your car satisfies the "Euro 4" pollution minimization standards, it is officially allowed in despite the traffic block. But one Italian colleague complained recently of the difficulty of explaining this to improperly trained police staff that are not aware of this particular "loophole".
And occasionally, for special occasions like a big soccer game, the traffic block is temporarily suspended.
So as you see, it is necessary to keep track of what blockages have been set up. Your best bet is your Italian colleagues - it is a daily discussion subject for who has to find alternative ways to get to work.
If you disregard the traffic ordinance and drive into a city that has been blocked for your license plates, and get caught, you will be looking at a fine of 72 Euros.