Some time back, we reported that Mexico City Mayor Marcelo Ebrard had decided to extend the controversial "Hoy No Circula" (Today Don't Drive) plan, a program where drivers are prohibited from using their vehicles one weekday a week based on their license plate numbers, to Saturday. The plan's objective, since its launch in 1989, has been to force drivers off the road and ostensibly reduce pollution. But many question whether the policy actually works. Some studies have shown that wealthier drivers simply take another car to work on the days when their principal car is banned.

This week an academic from the Mexican Academy of Sciences called Ebrard and other city politicians out on the failings of Hoy No Circula. "Simply put, the pollution in the city has not seen any effect correlated with the Hoy No Circula measure," said
Héctor Rivero Rotgé, researcher at the Physics Institute at Mexico's National Autonomous Universtiy. Rivero Rotgé and others also recently published an article in the journal Ciencia to the same effect. Meanwhile, city officials claim that the program has contributed to a drop in pollution, and that 2008 had the cleanest air quality on record in the last two decades.

Beginning in 2008, Hoy No Circula was extended to Saturday. One fifth of the city's 2.5 million registered vehicles will be restricted from circulating between 10 am to 6 pm. : Via Teorema Ambiental
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