What is the study process and how does it lead to the project brought to the public inquiry?

The studies in progress, known as "preliminary studies", are organised in two phases:

• The first phase aims to carry out a multi-criteria comparative analysis of the options studied (tunnel entrance, location of stations, configuration of the terminus, etc.), in the light of the technical studies and the observations expressed in the context of the consultation on the project. This analysis was presented at the consultation workshops in February/March 2025, sector by sector.
• The second phase aims to technically deepen the insertion and design of the structures for the preferential options, in order to converge towards a single extension scenario that will be presented to the public inquiry. The choice of options selected for further study at the end of the first phase of studies will be the subject of arbitration with the project's partner communities, which will be presented to the public by the summer of 2025.

The entire process, from studies to the public inquiry, is accompanied by continuous consultation under the aegis of a guarantor of the National Commission for Public Debate (CNDP).

For more details on the method and governance, you can refer to the educational sheet "The study process of an infrastructure project".