摘要：With an increasingly urban population, cities have an important role to play in global environmental sustainability. Cities engaged in pioneering and ongoing sustainability experimentation-the frontrunners-can lead the way towards sustainability transition, and often become the beacon for others to follow. However, the nature and the internal dynamics that make a city a frontrunner, or the role of frontrunner cities in sustainability transition beyond their boundary, remain unclear. In addition, most studies on the influence of these frontrunners are limited to passive influencing, i.e. how the practice has been duplicated by others, or how the practice is adopted and mainstreamed into system level. Based on in-depth case studies on a frontrunner city and two other cities influenced by it, this paper examines how momentum for positive changes has been initiated, built, and sustained towards changing the status quo of practice through a succession of actors and a series of reinforcing feedback loops. We argue that creating a positive inertia through sustained momentum and embedding the frontrunner identity in a city is essential for it to continue the process of sustainability transition. Frontrunners can create flow-on benefits for other cities through a proactive influencing. Supported by multiple two-way benefits, such proactive influencing is a new mechanism of mainstreaming and up-scaling urban sustainability experiments in system innovation and transition.
