During the last third of the 20th century, citizens throughout North America and Europe organized protests against urban highway projects, influencing urban transport planning in ways that shape its evolution to this day. With the globalization of car-centred urban planning models, some similar movements have emerged in developing countries. What, if anything, can they tell us about citizens’ role in innovation to achieve more socially just, good and livable cities? Using a multidisciplinary approach grounded in planning theory and a local adaptation of participatory action research methods, this study explores lessons from an anti-highway movement in Santiago, Chile (1997). This study contributes citizens’ perspective on crucial issues within the philosophy and history of city planning, examining shifts in governance that can significantly influence the potential for change in planning and city systems, even under adverse conditions. Is improving participation just a matter of ‘getting the process right’? This experience indicates that it requires re-formulating frameworks to encompass democratization, fostering multi-scalar, self-generating civil society organizations, and focusing on the role of organized citizens, rather than individuals, as they act on policy ecologies. The evidence from this Santiago case supports Portugali’s argument that planning is both a profession, exercised by especially trained ‘experts’, and a skill exercised by citizens working from their everyday expertise. This example explores the mechanisms through which, even in a relatively hostile environment, self-generated citizen organizations may play a significant role in contesting business-as-usual debates and achieving innovative policies favouring greater equality and sustainability.