[3][4] It consists of one single main tube hosting two circulation ways in opposite direction and one security gallery for emergency interventions and escape route in case of fire.

With the Mont Russelin tunnel, it makes possible to cross the last chain of the folded Jura (Les Rangiers) from the Swiss plateau to reach the Ajoie region.

The Mont Terri tunnel directly connects the near localities of Saint Ursanne (SSE) and Courgenay (NNW) and the cities of Delémont and Porrentruy.

The facilities consist of the underground Mont Terri Rock Laboratory [fr] conducting research on geological, hydrogeological, geochemical and geotechnical characterisation of Opalinus Clay, a 130 m thick and watertight argillaceous claystone deposited 174 million years ago during the Aalenian (Middle Jurassic epoch).

The project aims to share information and knowledge between Mont Terri partners and to prepare the deep geological disposal in Opalinus Clay at greater depth (-600 to -700 metres; 2000' to 2300') in the north of Switzerland in the area of Zurich in the decades to come.