Sihlquai|HB to the north next to exit Sihlquai via the most western underpass, tram lines , , and ; Bahnhofquai|HB to the east via the main hall, tram lines , , , , and trolleybus ; Bahnhofplatz|HB to the south via traverse hall, main hall, or underground ShopVille, tram lines , , , and trolleybus ; Bahnhofstrasse|HB just south of Bahnhofplatz via main hall or underground ShopVille, tram lines , , , and ; Sihlpost|HB 300m to the south-west from exit Europaallee via the most western underpass, tram lines , and trolleybus . Train operations Due to its central location in Switzerland and in Europe, the station was quickly able to establish itself as an important railway junction. Most trains running through several European countries operated through Switzerland. In addition, a majority of Swiss mainline trains travelled to or from Zürich. For the clock-face timetable introduced to Switzerland in 1982, Zürich is the "pacemaker". Delays and other disruptions at Zürich Hauptbahnhof sometimes affect the whole of Switzerland. Long-distance trains meet in Zürich on the hour and half-hour, and thus connect with each other. In cases of delays, connecting trains wait a maximum of 3 minutes beyond the scheduled departure time, except for some international trains and the late night trains. S-Bahn services do not wait for late connecting trains, but the long-distance trains - contrary to popular opinion - usually wait for delayed S-Bahn trains (also for a maximum of 3 minutes). Flood risk The Sihl passes through the station in a tunnel, with platforms above and below the river, and public circulation areas to either side. The tunnel comprises 5 culverts with a length of and a clear opening of by each. This limits the river's flow capacity, raising concerns about the capacity of the tunnel to deal with extreme flood events. Additionally, during the building of the new Löwenstrasse platforms, it was necessary to temporarily close part of this tunnel, thus reducing the capacity even further. Some upstream of the station lies the Sihlsee, Switzerland's largest artificial lake, which is impounded by a high dam. Studies showed that a failure of this dam could lead to an high flood wave reaching the Hauptbahnhof within 2 hours. This threat has led the City of Zürich to develop, publish and test evacuation plans for the affected areas of the city, and especially the station area. Customs Zurich main station is,