The 20 kilometres long section between St. Michel to Modane on the north side of the Mont Cenis Tunnel has a maximum inclination (gradient) of 3%, an average inclination of 2.1% and a smallest curvature radius of 350 metres. The erection of support structures in difficult areas with danger from landslides, and of tunnels with a total length of 4624 metres was necessary. The 41 kilometres long section between Bardonecchia and the south terminus of the Mont Cenis Tunnel has a maximum inclination of 3 per cent, an average inclination of 2.05% and a smallest curvature of radius of 450 metres. On this section 18 bridges and 26 tunnels with a total length of 8115 metres were built.