题目内容：
The northern Italian city of Milan banned all traffic from its streets for 10 hours on Sunday (26)reduce smog.The measure which was first imposed on a trial basis in the'year 2007 is (27)__________whenever pollution exceeds the statutory limit for 12 (28)__________ days.
Satellite imagery shows Milan to be one of the most polluted cities in Europe. An estimated 120,000 (29) will be affected by the move, according to the major daily newspaper in the city.
The most polluting vehicles have (30) __________ driving through the city center since Thursday. But on Sunday, there was supposed to be no traffic between 8:00 and 18:00.
The ban is imposed when pollution (31)__________50 micrograms of particulates per cubic meter of air over 12 days. The last time the full ban was (32) __________ was in February.
The move is not popular with all environmentalists, who argue that the city's public transport system should be improved to (33)__________people from using their cars. Local Green Party councilor Enrico Fedrighini said cars with three or four people inside should be offered free parking, for example. "One or two car-free Sundays each month will not do anything to (34)__________ the smog crisis," he told the daily newspaper in the city.
Public transport was to be bolstered during the day, with an (35)__________ metro trains and buses operating.
根据材料，回答问题。
26.__________
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