A police officer controls cars and scooters during the limited traffic day, in centeral Rome, on December 29, 2015. 
A second day with limited traffic of odd and even car plate numbers was enforced in the hope of lowering air pollution. A lack of rainfall has led pollution levels to climb in recent weeks, and has prompted the administration of Rome, to appeal to drivers to respect the rules.    / AFP / ANDREAS SOLARO        (Photo credit should read ANDREAS SOLARO/AFP via Getty Images)