Bogotá, traditionally portrayed in the 1980s and early 1990s as an urban dystopia and a city of fear, has become a global model of green urbanism in less than a decade. Since 2001, cities as diverse as Jakarta, Guangzhou or Los Angeles among more than one hundred others, have implemented a Bus Rapid Transit (BRT) system drawing inspiration from Bogotá’s Transmilenio BRT. In the same time period, mayors, transportation planners and bike advocates in more than 120 cities have referenced Ciclovía, a 70-mile weekly car-free event in Bogotá, to pass local street closure program in their home cities. Although urbanism has been shaped by policies and planning mechanisms drawn from European and North American cities for centuries, the rapid spread of Bogotá’s Transmilenio and Ciclovía in the last decade suggest: 1) a significant increase in the speed of urban policy circulation; and 2) that the current transnational traffic of urban policy knowledge and ideas of the “good city” is more complex than a simple North-to-South transfer. In my dissertation, I hypothesize that the rapid circulation of urban policies and urban best practices marks the emergence of an increasingly transnational political arena within urban politics, what I call the politics of policy circulation. In the politics of policy circulation, a set of situated local policy actors —broadly defined as to include mayors, planners, NGOs, consultants, or activists among others—use trans-local and transnational connections to mobilize other cities’ policies in efforts to achieve increased legitimacy for their own agendas in their home cities. I use this framework to examine the politics behind the construction and circulation of Bogotá’s Transmilenio and Ciclovía as international “best practices” in green urbanism and the different ways in which they were mobilized, contested, and transformed in Guadalajara (Mexico) and San Francisco (California).