Cost-benefit analysis is today the subject of many criticisms and has been widely debated. Despite these concerns, it remains one of the main methods for the evaluation of public policies, in particular, in transport. This method is rooted in the debates on the measurement of public utility between the engineers of the Corps des Ponts et Chaussées in the nineteenth century and, in particular, within the work of Jules Dupuit. In this chapter, Philippe Poinsot traces Dupuit’s contribution to the measurement of public utility, placing his research in a broader perspective, and clarifying the relationships between public utility and another important concept for engineers known as “intérêt general.” This distinction is important to understand Dupuit’s position on many subjects related to economics and regional science.