The merger of the RSG with the Saignelégier–La Chaux-de-Fonds Railway (SC), the Tavannes–Noirmont Railway ("Chemin de fer Tavannes–Noirmont", CTN) and the Régional Porrentruy–Bonfol (RPB) to form the Chemins de fer du Jura, which was completed on 1 January 1944, created the basis for a radical renewal of the line.