b. alessandra orofino: our mobility systems, in general -- very few exceptions -- suck.bility system, you preclude entire segments of the city from living the city. from actually accessing the opportunity and the beautifulness and the amazingness that city has. because it is hard for them to get around. you also preclude the rich people in the city from getting to know other areas of the city, which can be exciting and fulfilling experience in itself. so you are creating a city in which everyone is living in their own territory, which is terrible. narrator: at the forefront of these infrastructure problems are the city's poor. they can become physically cut off from the economic opportunities living in a city provides. alessandra orofino: it includes rapid expansion of cities. the fact that in the developing world, one third of the population is living in slums, something none of us should accept as we grow and think about a planet in which we want to live. narrator: slums are a result of rapid, unplanned expansion. today, an estimated 863 million people live in slums. i