Around the world, cities are the “ground zero” of inequality and unsustainability. The two largest cities in the United States, New York City and Los Angeles, are also the two most unequal cities, and one-third of the United Kingdom’s poorest 10% of families live in London. Meanwhile, two-thirds of the world’s energy and 70% of global carbon emissions are attributed to cities. This leads to the question of how the evolution of public policy, and urban design, can strategically combat these two growing issues. Around the world, cities are looking to mobility as part of the solution, and in particular, asking a simple question: what if public transport was free?