The public inquiry on the project to extend line 1 to Val de Fontenay was held from 31 January to 2 March 2022 under the aegis of an independent commission of inquiry, chaired by Mr Jean-Pierre Chaulet, and composed of 4 full members: Mr Jean-François Biechler, Mr Jordan Bonaty, Mr Alain Charliac and Ms Nicole Soilly. Prior to the declaration of public utility, it constituted a new stage of public participation which had the following aims:

• Present the characteristics of the project and the conditions for its integration into its environment, its impacts and the measures to remedy them;
• To collect the public's opinion in order to provide useful information for the assessment of the project and to refine the continuation of the studies.

The independent commission of inquiry has drawn up a report on the progress of the public inquiry and has given its opinion on the extension project.

From January 31 to March 2, 2022, several modalities were available to the public:

• Opinions could be submitted on the digital register, and on the paper registers in the town halls of Fontenay-sous-Bois, Montreuil, Neuilly-Plaisance, Paris 12th and Vincennes, in the Prefectures of Paris, Seine-Saint-Denis and Val-de-Marne, or sent directly to the commission of inquiry by email or post.
• 14 sessions to discuss with the commission of inquiry have been organised in Fontenay-sous-Bois, Montreuil, Neuilly-Plaisance, Paris 12th arrondissement and Vincennes.
• 3 public meetings were held in the presence of the project owner and the commission of inquiry, on 10, 15 and 24 February 2022.
• The public inquiry file was available for consultation in town halls and prefectures and remains accessible on the project's website, in the media library.