Résumé en anglais

Cost–benefit analysis (CBA) is a tool used to evaluate the potential socio-economic impact of public investment choices. In many countries, particularly in France, this tool is used to support decision-making related to transportation infrastructure. In the context of difficult budgetary arbitrations, taking the multiple effects of the different choices into account makes choosing among transport infrastructure investments a two-fold problem. On the one hand, public decision-makers have limited resources that they must use in the best way possible. On the other hand, when choosing among alternative investment projects, the decision-makers reveal their priorities (based on the importance they assign to the different projects), and these priorities must be perceived as legitimate. Based on a case study of how French institutions use the CBA method, this paper examines how the use of cost–benefit analysis interacts with the use of public debate and stakeholder participation in France today. This French case illustrates the difficulty of striking the right balance between the expert knowledge produced by CBA methods and the knowledge produced by the participation of various stakeholders in the decision-making process.