The construction of the 4.5 km long bypass between the roundabout Säli and the connection to the Mittelgäustrasse close to Rickenbach presents an important step to solve the regional traffic congestion in the region of Olten. The 45 m long cut and cover section is directly followed by the bored tunnel section and underpasses two existing industrial tracks. For the planned works, the tracks can be put out of service for only short time periods. Therefore, and because of the geometry of the track system, the cut and cover section was constructed using the top-down method, whereupon the excavation underneath the cover was performed. The cut and cover profile is designed as a rigid closed frame structure; it is partly located 3 m below the groundwater level, so that it had to be designed as a waterproof concrete structure.