La Redoute Overpass is a masonry arch structure built in the 1920s. The existing bridge crosses the SBB railway cutting through which the two Lausanne-Geneva railway tracks pass. The existing structure, with a width of 3.70 m, accommodates only a single traffic lane. Furthermore, the masonry arch does not allow the widening of the railway cutting required for the construction of a third railway track.

INGPHI was commissioned by the City of Nyon to design and construct a new structure incorporating the new road and railway operational requirements. The selected solution consisted of building a new bridge above the existing arch. First, new pile foundations were constructed behind the existing bridge. Subsequently, the two prestressed reinforced concrete girders were prefabricated on site, one after the other, using the existing deck as a working and formwork platform. The girders were installed on either side of the existing structure using mobile cranes during two night-time possession operations, during which railway traffic was suspended. The concrete deck slab, waterproofing works and pavement works were then completed.

The project was carried out in collaboration with the municipalities of Nyon and Prangins and with SBB. All measures were implemented during both the design and construction phases to ensure the safety of railway operations. Although no longer in service, the existing masonry arch will be maintained until railway operational measures are scheduled for its demolition.