Sao Paulo,Brazil (population: more than eighteen million)
Many people work in the center ot Sao Paulo,but they don't live there.
They've spread out to neighborhoods outside the city, where housing is cheaper.
Every day,these people travel into the city,and traffic is very heavy.
First,they are building better subways.
Another goal is to make it cheaper for people to live in the downtown area.
Doing this will shorten the distance people travel for work and reduce traffic and pollution in the city.