Ecobici stations can be found all over the city. For those with a membership, it's a very simple system. Borrow a bike a one location; return it to any other Ecobici rack. To further help fight the tremendous air pollution problem Mexico City faces, on Sundays, many downtown streets are closed to traffic and only permit bicycle or pedestrian usage. Increased, efficient public transportation like the more rapid Metrobus further promotes a greener DF.