The picturesque town of Grüningen has been subject to traffic congestion for many decades. In 2018, a design competition was set up by the local authorities to invite proposals for a bypass, including new crossings over the adjacent valley.
Calatrava’s design, comprising a ring road with two new bridges for pedestrian and road traffic respectively, was selected as the winner for its elegant approach to solving the problems of traffic congestion.
Grüningen is a historic town founded in the Middle Ages and situated on a hill upon which a Medieval castle and church were built. The town is surrounded by a valley which would have provided a strategic and defensive advantage at the time. Indeed, the Grüningen town centre is historically significant and for this reason it is a protected site in terms of architectural and archaeological heritage.
Since the town is located on traditional transportation route, traffic has been crossing its centre for hundreds of years. Today, the large increase in traffic volumes (principally buses and cars), has become an unsustainable burden for the town, leading to the proposal for a much-needed ring road.
The current access to the town is via a large dam which divides the valley into two independent parts. The dam was constructed over 100 years ago without any geographical, scenic or even historical sensibility.
Calatrava’s proposal is not simply to establish a new route on top of the existing transport network, but rather to carry out an urban intervention which aims to release Grüningen from its restrictive condition, easing traffic flows in the town centre without overloading peripheral areas.
To solve these challenges, Calatrava’s design includes two new bridges over the valley. The first is a pedestrian bridge capable of accommodating limited road traffic. It will replace the dam, thereby recovering the continuity in the valley and allowing a clear reading of the historical position of the old town. This approach will also preserve the existing recreational areas around the town centre.
The second bridge will be a dedicated traffic bridge which crosses the valley at a relatively low level, safeguarding the views to the old town from the environs. The bridge will be connected to an underground passage, based on economical ‘cut-and-cover’ construction, and most of the existing traffic flows will be diverted along this route.
The bridges are of similar form and aesthetic, each vaulting over the valley below with shallow and slender arches, creating elegant and harmonious new infrastructure. The two arches on each bridge are inclined in the transverse direction, allowing them to land on a single support at each end, minimising the contact area on the sides of the valley and reducing the shadow cast upon it.
The fact that the bridges are effectively ‘twins’ in their external character facilitates their joint integration into the landscape, a recurring theme in many Swiss bridges such as the Devil's Bridges in the Gotthard pass or the numerous bridges along the Glacier Express route.
After the removal of the existing dam, the lightness of the two bridges will return the historic centre of Grüningen to its original geographical context: standing as a fortification at the top of the hill, surrounded and protected by a continuous valley below.