While the method described in this article is applicable to various types of public facilities, the focus here is on infrastructure investment in transportation. The authors examine the link between economic and financial assessments. The goal is to optimize social returns as defined in cost-benefit analysis, but making allowance for two over-neglected aspects: (1) the fact that most of the large-scale investment projects envisaged will be co-financed by users and taxpayers, as recent investments have been; (2) the need to think in terms of deciding not only on the best project but also on the best program of projects. This article shows the attractiveness of “collective utility per public euro invested” as a criterion for measuring the effects of the intensification of the public-finance constraint.