Distribution of cars in the Italian city of Bologna 2017, by emission standard

In 2017, Euro 6 cars made up about 20 percent of the automobile fleet in Bologna. Euro 4 and Euro 5 cars combined made up over 50 percent of the total number of cars, while the Euro 0 class, the most polluting kind, accounted for six percent of the automobiles in the city.于2017年，博洛尼亚的汽车车队中，欧六标准汽车约占20%。而欧四和欧五标准汽车的总数占据了超过50%，同时，污染最为严重的欧零标准汽车在市内汽车总数中占比达到6%。