The portion of automobiles with unleaded gas catalytic converters expanded in the Chilean capital from 36 percent of the total in 1992 to 59 percent last year, says the National Institute of Statistics. In 1993 there were 180,000 unleaded gas-burning cars in Santiago, while in 2002 the figure rose to 525,700.

Emissions of pollutants by engines with catalytic converters are 80 percent lower than conventional motors that burn leaded gasoline.

Since 2000, cars with the “green stamp” are free from the traffic restrictions implemented when states of environmental pre-emergency and emergency are announced as a result of the city's chronic air pollution problem.