Poya Bridge

The Poya Bridge, known locally as the Poyabrücke, is a striking architectural marvel that spans the Sarine River in the picturesque city of Fribourg, Switzerland. Officially opened to traffic on October 12, 2014, this impressive structure is a vital segment of the Swiss Route 12, seamlessly connecting different parts of the city while offering breathtaking views of the surrounding landscape.

The Location and Structure

Stretching an impressive 851.6 meters in length, the Poya Bridge begins its journey from the La Cité-Bellevue neighborhood on the right bank of the Sarine. From there, it ventures northwest, soaring 70 meters above the river valley and the industrial district of Les Neigles. Below this modern cable-stayed bridge, the Route des Neigles road bridge also crosses the river, which transitions into the Schiffenensee in this area. The final stretch of the bridge ascends the steep slope above the lake, culminating in a left curve that leads into the St-Léonard Tunnel. This tunnel passes under the Lausanne-Bern railway line and connects to the underground link with Murtenstrasse.

A Historical Perspective

Fribourg has a rich history of bridge construction, dating back to the Middle Ages when several bridges were built over the Sarine and the Galtera. The city also has experience with suspension bridges since the 19th century, as evidenced by the Zähringer Bridge. The old road from Bern to western Switzerland once traversed the city, crossing the river with bridges. However, the post-World War II traffic boom overwhelmed the old town, prompting the city and canton to explore bypass routes. Numerous studies for a new river crossing emerged since 1959. Despite the opening of the Düdingen-Matran section of the A12 motorway in 1971, plans for a new city bridge continued. The new road connection between Murtenstrasse (Route 182) in the northwest and Bernstrasse (Route 12) in the east aimed to close the Zähringer Bridge to private traffic and alleviate through traffic in the old town around St. Nicholas Cathedral. It was estimated that around 25,000 vehicles would cross the Poya Bridge daily.

The Design and Construction

In 1989, the city of Fribourg invited five engineering consortiums to compete for the new road connection and the Poya Bridge. The submitted designs were evaluated based on concept and construction technique, aesthetics and integration into the urban environment, traffic and safety, and economic viability. The winning project, a collaboration between GVH (P. Gorgé, A. Vaucher, B. Houriet), Brugger & Clément & Collaud, Zwahlen & Mayr, and Schneider & Chablais, was developed into a detailed preliminary project and presented to federal, cantonal, and city authorities.

In 1995, the construction project was transferred from the city to the canton of Fribourg, which classified the Poya Bridge as a cantonal road H 182. In 1997, the federal government classified the bridge as part of the Swiss main road network and rerouted Route 12 around the old town of Fribourg. The construction project was publicly announced in autumn 1999. The Federal Commission for Monument Preservation and the Cantonal Cultural Heritage Commission demanded a route change further away from the villa known as Château de la Poya. Additionally, new safety standards for tunnel construction required a minimum distance between a tunnel exit and the next intersection. Consequently, the previously planned route with the tunnel in the St-Léonard district had to be extensively revised. The resulting project, including the bridge, tunnel, and an underground roundabout connecting the main roads, was eventually implemented.

Engineering Marvel

The central section of the 851-meter-long cable-stayed bridge boasts Switzerland's longest span at 196 meters. The two side cable-stayed sections span 86 meters each, while the side spans range from 35 to 54 meters. The bridge features three lanes for motorized traffic and a 3.5-meter-wide lane for pedestrians and cyclists. It has a constant gradient of 2%, rising from 592 meters above sea level at the western end to 609 meters above sea level at the eastern end. The first 160 meters of the bridge adjacent to the tunnel on the west side are covered with noise protection.

The floating bridge has a semi-fan cable arrangement for the central section. The side viaducts form a continuous beam. The pylons are monolithically connected to the deck slab to provide the necessary longitudinal stability. The construction of the Poya Bridge involved 44,000 cubic meters of excavation, 16,000 cubic meters of concrete, 2,800 tons of reinforcement, 3,530 tons of steel structure, and 177 tons of stay cables. The structure is secured by 720 anchors.

Financial Aspects

The estimated cost for the entire expansion, including the bridge, was CHF 211 million in May 2012. The financial coverage from the originally approved cantonal and federal contributions, a project change at the St-Léonard junction, and inflation amounted to CHF 179.4 million. In the referendum on September 24, 2006, the voters of the canton of Fribourg approved the cantonal contribution of CHF 58 million (adjusted for inflation to CHF 65.2 million) for the bridge and access road construction with an 81% approval rate. At that time, total costs of CHF 120 million (excluding inflation) were expected.

In conclusion, the Poya Bridge is not just a feat of modern engineering but also a symbol of Fribourg's dedication to preserving its historical charm while embracing the future. Its sleek design and strategic importance make it a must-see landmark for anyone visiting this beautiful Swiss city.