For the people of Rosenheim themselves, the superlative would not have been necessary. Many people in the Upper Bavarian city of 65,000 people have been waiting all these years to finally get rid of some of the excessive through traffic. This should succeed with the Rosenheim west tangent. According to the state building authority, its central structure, the 670 meter long Aicherpark Bridge, has become the longest bridge on federal or state roads in Bavaria. Traffic has been passing through them since this Thursday.
Plans for this new route for the B 15 have been in existence for a very long time; at least the rough route of the Rosenheim West Tangente has been known since the end of the 1970s. But the bypass has only really been built since 2012, initially until 2015 on a first section in the south from the new Rosenheim West exit on the A 8 to the western outskirts of the city towards Kolbermoor. At the other end in the north, a bypass was created for the small town of Pfaffenhofen am Inn. The Aicherpark Bridge, which began in 2015 and has now been opened, turned out to be much more difficult for planners and construction companies. It not only leads over the eponymous industrial area and the Holzkirchen-Rosenheim railway line, but also over the Mangfall and the Mangfall Canal immediately next to it in the form of a cable-stayed bridge.
For the foundations of this bridge, the engineers had to develop a new type of foundation with scientific help from the Technical University of Munich, which cost two to three additional years and therefore a lot of additional money. The subsoil in the Rosenheim Basin consists of soft, unstable lake clay – a thick layer of sediments that settled in a huge lake after the last Ice Age glaciers retreated from the foothills of the Alps. In order to build a bridge on it, it had to be constructed as light as possible – and at the same time, dozens of huge concrete piles had to be sunk up to 50 meters deep into the ground to ensure proper support. The connection point for Aicherpark, which floats above the ground and has curved ramps, is also based on this specially developed “Rosenheim mixed foundation”.
All of this has caused the costs for the entire project to rise to an impressive 263.5 million euros. This has to be paid for by the federal government, which decided in 2012 to finance this and a handful of other projects from a newly launched special pot filled with one billion euros. Accordingly, the ribbon that was cut by a number of politicians on Thursday on the Aicherpark Bridge was not white and blue, but black, red and gold. Michael Theurer (FDP), Parliamentary State Secretary in the Federal Ministry of Transport, once again promised the people of Rosenheim “more traffic safety and less noise”.
Along with the bridge, a piece of relatively normally built road was opened to traffic on Thursday, so that the western bypass has been extended by a total of four and a half kilometers and a noticeable relief can now be expected, at least for the west of Rosenheim. The State Building Authority is initially expecting around 6,000 fewer vehicles per day on the busy Outer Münchner Straße.
However, the 11.3 kilometer long western bypass is not yet completely finished. There are 1.3 kilometers missing as the last northern gap, but it is also quite challenging in terms of construction. There, near the hamlet of Wernhardsberg, the route has to cross under the important Munich-Rosenheim railway line – also in the soft lake tone and with constant railway operations with trains running almost every minute at times. This section has also been under construction for a long time and should ideally be finished by the end of 2025.