Description: The 4.4 km long Uetliberg Tunnel, connecting the Birmensdorf bypass (N20.1.4) in the west with the existing Zurich-Chur highway (A3 motorway) in the east, is the key structure of the new Zurich western bypass. The project consists of two parallel tubes, each about 4.4 km long, which both increase in slope by approx. 1.6 % between the east and the west portals. Stations with equipment and installation rooms will be built at both the west and east portals. The underground central ventilation station is located in the Reppisch Valley (Stallikon).