The 10:00 am to 6:00 pm ban was also imposed in Alessandria, Vercelli, Varese, Cremona, Trento, Frosinone and Verona.
The five regions in which these towns are located frequently record pollution levels higher than European norms.
A similar measure was taken in Rome and Milan over the last week, with traffic being restricted to odd-numbered registration plates one day and even ones the next.
There are some 32 million cars on the roads in Italy, which has a population of 58 million.