The adantages of limiting your car useage is sgood becauce it brings down pollution in the air. As a result 70 pecent of Vauban's familes do not own cars, and 57 percent sold a car to move here. "when i had a car i was always tense. I'm much happier this way," said Heidrun Walter,a median trainer and a mother of two. 12 percent of green house gas emissions in Europe... and up to 50 percent in some car-intensive areas in the United Staes. Beijing,China, which is known as one of the most polluted cites in the world. Millions of Colmbians hicked, biked, skated or took buses to work during  a car-free day yesterday, leaving the streets of this capital city eerfilydevoid of traffic jams.  People particapated in the event when it was raining. Two other Colombian cities, Cali and Valledupar, joined the event. "Its a good opportunity to take away stress and lower air pollution," said businessman Carlos Arturo Plaza as he rode a two-seat bicycle with his wife. The day without cars is part of an improvement campaign that began in the Bogta in the mid-1900s. Its has seen the construction of 118 miles of bicycle paths, the most of any Latin American city, according to Mockus, the city's mayor. We should try to decrease pollution by riding bike, skating, walikng more then using our cars to get us somewhere. Accoridnig to the article '' All of our development since world war II has been centered on the car, and that will have to change'', said David Goldberg, am offical of Transportation for America, a fast growing coalition of hunders of grouos in the United States ... who are prmoting new communities that are less dependent on cars. Goldberg added " how much you drive is as important as wether you have a hybird.