São Paulo Clean City Law

In 2007, the world's fourth-largest metropolis and Brazil's most important city, São Paulo, became the first city outside of the communist world to put into effect a radical, near-complete ban on outdoor advertising. São Paulo: surveys indicate that the measure is extremely popular with the city's residents, with more than 70 percent approval.

But you still get advertising in underground stations. So what's the difference? Why is it allowed in underground places? Advertising is actually more effective in underground places because you have nowhere else to look, so a kind of contradiction appears.


Useful links:
http://www.adbusters.org/magazine/73/Sao_Paulo_A_City_Without_Ads.html
http://www.flickr.com/photos/tonydemarco/sets/72157600075508212/
http://www.flickr.com/photos/tonydemarco/sets/72157609118511046/