The work to improve the platform and environmental treatment of this tourist route is being carried out on a 17.2 km stretch of the N-621 between Castro Cillorigo and Panes. The first section, which has just been opened to traffic, is 0.5 km long and another 0.6 km is planned to be opened during the summer. The winding route to be improved runs through the steep Desfiladero de La Hermida (between the regions of Cantabria and Asturias), and is the only access route from the Cantabrian coast to the valleys of Camaleño, Liébana and Picos de Europa. It has an average daily traffic volume of 2,500 vehicles, which occasionally triples during the summer months due to the natural and scenic interest of the area. The road runs between the slopes of the Picos de Europa and the course of the river Deva, which it crosses four times with single-span bridges which have already been widened in a previous project by Grupo Puentes. The project takes place in a natural environment with several protected areas, which has been the main conditioning factor in the design. The solution adopted in the open section involves widening the platform towards the river, to achieve a platform width of 8 m, thus rectifying the layout of several curves, which will have two three-metre lanes and two one-metre verges. The different solutions to be implemented consist of breakwater walls, concrete walls, cantilevers of varying widths and concrete structures to be used in the construction of the bridge
