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MEXICO CITY – Mexico City is ordering 40 percent of cars and trucks to stay off the streets Thursday, extending for a third day a traffic cutback aimed at lessening pollution.
Under a rule in effect through June, one-fifth of the city's vehicles normally must stay at home on a weekday, with the day determined by license plate numbers.
But on Wednesday, smog stayed above 1½ times acceptable limits for a third straight day, meaning an additional 20 percent of vehicles can't be used Thursday.
Ozone, a key component of smog, reached almost 1.8 times acceptable limits.
Before the rule was implemented last month, newer or cleaner cars were exempt from the one-day driving ban.
The pollution spike is due to seasonal weather patterns and the increasing number of cars in the city.