Megacities around the world face the same problems: traffic and housing. Sao Paolo, Brazil, is a good example. "There are 30 million daily trips in Sao Paolo," says Jorge Wilheim, a city official. "One-third is public transport, one-third is private cars, and one-third is walking. Sixty to seventy percent should be on public transportation." The city is building a new freeway and adding to the subway system, but it's slow work. Ever day, millions of people are sitting in traffic jams.