This article draws on a case study of organisation–citizen engagement during railway infrastructure planning in southwest France, to examine the nature of participatory democracy, both conceptually—as elucidated by Habermas and others—and empirically, as recently practised within the framework of a model established in one democratically governed country. We analyse roles played by the state organisation responsible for building railway infrastructure; the National Commission for Public Debate; and the Garants, who oversee and facilitate the participatory process as laid down by the French law of Public Debate. We conclude by arguing that despite its normative aspects and its lack of provision for analysis of power relations, Habermas’s theory of communicative action can be used to evaluate the quality of organisation–citizen engagement, potentially providing a basis for informing actual models of democratic participation.