AP Photo

Innovative public transport solutions like this will be needed in the denser megacities of the new urban age. The planet is moving towards two billion cars. Commuters in Brazil's biggest city, Sao Paulo, can sit in traffic jams of up to 180km (110 miles). Americans currently spend an average of nine years of their lives sitting in their cars. China, meanwhile, is now the world’s biggest car market, with ownership going up 20-fold since 2000, and many of its cities’ new six-lane highways are already clogged with traffic and car fumes.