Planning transport infrastructures in an uncertain context. Analysis and limits to contemporary planning in France.

International audienceIntroduction : The planning of transport infrastructures in France has been marked by three major developments: the European reform concerning the opening of rail transport to competition, the privatisation of semi-public motorway concession-holding companies, and the use of public-private partnership contracts. This article proposes examining the following research question: how to plan a series of infrastructure projects within an uncertain context? The methodology (i) analyses whether the objectives (traffic, travel time, safety, cost, socio-economic profitability, financial profitability) of the 12 motorway and HSL projects built since the 1990s have been attained with the new planning procedure (such as risk management methods, financial risk assessment, impact assessment, public consultation) (ii) compares the additional costs and delays for three HSL projects according to their type of financing and whether or not they have used these planning procedures. Results The analysis shows that traffic levels are lower thanforecasts for 8 projects. The cost is greater than the forecasts for all infrastructures. The socio-economic profitability and the financial profitability are also lower than forecasts for approximately two-thirds of the projects.Conclusion The social, political, institutional and environmental risks are generally well identified and treated by the client, no matter whether public or private.. The risk of additional cost is less well covered. The traffic risk remains a topical issue. Anticipating risks is liable to produce other risks, such as overcosts or opposition. It seems necessary to deepen the traffic forecast studies and to develop the multi criteria analysis method that can take account of the different points of view from the consultation