The Le Croci tunnel is a total of about 1670 m long and has an underground escape passage between the invert and the road surface. The road surface is connected with the underground passage via special pedestrian passages found in safety niches suitably equipped for emergencies. The rock formations encountered in building the Le Croci tunnel consist essentially of Monte Morello (alternate marly limestones, malms, clay marls and laminated argillites) and the argillites in the Sillano area (alternate highly laminated marly slates and calcarenites) in their various facies. The water table is above the height of the crown almost everywhere. The maximum ground cover is about 90 m, and the minimum (2 m approx.) is found at a fault in Monte Morello. An intermediate service tunnel is to be dug in this area, which is just before the existing A1 underpass, to create an artificial lay-by and bypass link road with the other motorway carriageway.
The adjoining Case Forno tunnel is to have an overall length of about 193 m and will also house the new southbound carriageway. The tunnel passes through high ground about 370 m above sea level with substrates consisting of argillites belonging to the Sillano formation, under its alteration horizon consisting of a layer nearer the surface of eluvial-colluvial deposits.