Cars were banished Monday from the streets of Milan while in Rome every second vehicle was forced off the road as Italian authorities battled a buildup of smog after a spell of unseasonably dry, calm weather.
In Milan and the nearby town of Pavia, no cars will be allowed onto the roads between 10:00 am and 4:00 pm for three days starting Monday, while in Rome owners of cars with odd-numbered plates were ordered to leave them at home for the day.
On Tuesday, cars with even-numbered plates will be targeted under an alternate traffic measure used three times this month to try improve air quality in the capital.
Traffic restrictions were also in place in the southern city of Naples, where only vehicles operating to Euro 4 emissions standards or higher are allowed circulate this week.
With most Italians on holiday between Christmas and New Year, the measures were seen as largely symbolic.
"This morning, the streets were deserted but it's not only because of the driving ban. Am I the only person working this Monday?" one Milan resident wrote on Twitter.