The Zurich Underground Railway, or Zurich U-Bahn, was a project started in the 1970s to build a rapid transit network in the Swiss city of Zurich and several bordering municipalities. This project was itself preceded by several earlier plans dating from between 1864 and 1959. In April 1962, the "Tiefbahn" (lit. "deep rail") project was proposed, which would have included placing the Zürich trams underground in the city centre by building 21.15 km of underground lines, this was rejected in a referendum before any construction had been undertaken.

In the 1970s "U-Bahn" project, the first line would have led from Dietikon via Schlieren, Zürich HB, Oerlikon and Opfikon to Zurich Airport, including two short branch lines to Schwamendingen and Kloten. The two most important development axes of the agglomeration, Limmattal and Glattal, would have been joined onto the network. The line would have been 27.5 km long, 14.8 km of which would have been underground. At a later point in time the construction of two more lines was planned. In spite of initial optimism the project was rejected in a referendum by the voters in the canton of Zürich. Some parts of the lines, which had been built as preliminary work for the Underground that was never realised, are used today as the Milchbuck-Schwamendingen tram tunnel and as the terminus of the Sihltal Zürich Uetliberg Bahn.

Although the U-Bahn project was never completed, little opposition was expressed against the suburban rail lines that were proposed at the same time to complement the U-Bahn. These proposals eventually evolved into the current Zurich S-Bahn system, which uses several newly built tunnels to pass under both the city centre and adjoining hills.

Initial plans

In 1864, one year after the opening of the Metropolitan Railway in London, the Zürcherische Freitagszeitung (Zürich Friday Journal) published the visionary idea of a partly underground steam railway that was to go from the main station, along the Fröschengraben and end at Lake Zurich. However, the moat was filled up and became the Bahnhofstrasse instead. At the beginning of the 1930s, the development of the Zurich tramway network was by and large completed and newly built districts became accessible by bus and trolleybus lines. City architect Herbert Steiner, who had developed the Zurich building and zoning regulations in 1948, predicted that 550,000 people would be living in the city. He deemed the disentanglement of traffic streams and the massive expansion of public transport essential in order to realize the ideal of a garden city. However, in his opinion the city was and would always be too small for an underground railway. Architect Armin Meili and geographer Hans Carol held similar views, but due to the imminent post-war economic boom (Golden Age of Capitalism) and mass motorization, their voices remained almost unheard.Hans-Rudolf Galliker: Tramstadt. S. 204–205.

In 1946, Kurt Wiesinger, professor of engineering at the ETH Zürich, put forward plans for a highspeed train that would have covered the distance between Zurich main station and Oerlikon in two minutes. Architect Wolfgang Nägeli presented a more realistic project in the Schweizerische Bauzeitung in 1947. Several tramlines were to be relocated underground in the city centre. He proposed building a tunnel underneath the Bahnhofsstrasse between Bürkliplatz and the Platzspitz park, along with lines branching off from Paradeplatz to Sihlstrasse and from the main station to Weinbergstrasse. This first draft comprised 2.7 kilometres of tunnels, as well as 0.2 kilometres of ramps and bridges. He calculated the costs would be between 35 and 40 million Swiss Francs. In a second step, he planned a second stage from Weinbergstraße to Beckenhof covering 1.1 kilometres of distance (plus 0.7 kilometres for ramps) and costing another 14 to 18 million Swiss Francs.

On 28 March 1949, a private "initiative committee for an Underground Railway in Zurich", led by construction engineer Adolf Weber, submitted an application for a constructing and operating concession to the Federal Post and Railway Department. The plan was to build a widespread underground network which would cover 158 stations and have a length of 107 km – including lines from Zurich to Küsnacht, Witikon, Dübendorf, Kloten, Weiningen, Dietikon, Sellenbüren, Adliswil and Thalwil. After revision, the overall length was reduced to 90 km. The required capital investment of approximately two billion Swiss francs was to be supplied from private investors, at an interest rate partly guaranteed by the state. Considering the horrendous costs, an acceptance of the application by the Federal Assembly seemed to be unfeasible. Thus, the proposal was withdrawn.Bundesblatt Nr. 39/1972, S. 573.

On 30 May 1959, another committee handed in two civic appeals concerning the "realization of the Zurich underground on behalf of all voters". The first one addressed the city parliament (legislative authority) asking for the provision of 200 000 Swiss Francs that would be used for a report on two underground lines (Enge – Kloten and Altstetten – Tiefenbrunnen), with a total length of 19.7 kilometres. Since that type of appeal falls under the responsibility of the city council (executive authority), it was dismissed. The second one instructed the city council to solve traffic problems, in a way it would have enabled establishing an operating company for the Zurich underground on a public economical basis. As the city council had already commissioned a report for similar routes, it advised the voters to turn that request down. In the following election campaign there were several opinions saying that the plans were unrealistic and not properly thought through. According to them, Zürich didn't have the required size for an underground system and the costs ware too high. On election day, 14 February 1960, 69.8% (48'502: 20'944 votes) voted against the Zurich underground.Bundesblatt Nr. 39/1972, S. 573–574.

The Premetro Project Apart from these private initiatives, the authorities were also engaged in long-term transportation planning. In 1952, the city council commissioned two teams of experts to devise a general traffic management plan, one of which was led by Carl Pirath and Max Erich Feuchtinger of the University of Stuttgart, the other by Kurt Leibbrand and Philipp Kremer of the ETH Zurich. Their task was to find a solution to Zürich's traffic problems that should last until the 1980s. The calculations were done with a number of 555,000 inhabitants living in the city and more than one million in the urban agglomeration. The proposals presented by both teams in 1955 had several points in common. High-capacity corridors were to be created for motorized private transport and junctions to be disentangled by over- and underpasses, elevated roads and tunnels. The tramway was to be kept as the backbone of the local passenger transport and supplemented by underground routes. However, the two plans differed widely in one point: Pirath/Feuchtinger proposed an extensive light railway network, which could be transformed into a full underground network later on. Leibbrand/Kremer on the other hand wanted to realize a smaller premetro network in the inner city, known in Zürich as the 'Tiefbahn'.Hans-Rudolf Galliker: Tramstadt. S. 210–211.

The publication of the reports caused an intense debate over transport policy. While the expansion of the street network was uncontroversial, the public transport proposals provoked long-lasting discussions. The city council preferred the moderate project suggested by Leibbrand/Kremer. The city parliament, on the other hand, preferred the wide-ranging project suggested by Pirath/Feuchtinger.Hans-Rudolf Galliker: Tramstadt. S. 213–214. In 1956, professor Walther Lambert was hired as an additional consultant for network design and operational management. In March 1957, a technical committee was appointed as well. Finally, city council and city parliament reached an agreement to work out an underground project of their own. This task was handed over to a working group, which was led by city councilor Walter Thomann and the director of the VBZ, Werner Latscha. In addition to Kurt Leibbrand, the working group also included representatives of several underground construction and engineering companies.Das Projekt einer Tiefbahn für Zürich. Schweizerische Bauzeitung 79/47 (1961), S. 847. In January 1961, the city council presented a project which consisted of tunnel sections with a total length of 12.3 km. The costs (excluding land acquisition) were estimated at around 329 million Swiss francs. In December of the same year, the city council added a further stipulation: The underground network was to have a length of 21.15 km at a cost of 544 million Swiss francs. As an extension to the original project, sections to Oerlikon and Schwamendingen had been added, as well as smaller modifications in the city centre.Hans-Rudolf Galliker: Tramstadt. S. 214.

The following tunnel routes were planned: Broschüre des Aktionskomitees Pro Tiefbahn Kalkbreite/Birmensdorferstrasse – Stauffacher – Sihlporte – Löwenplatz – Zürich Hauptbahnhof (main station) – Limmatstrasse Sihlporte – Talacker – Paradeplatz – Bellevue – Seefeldstrasse/Kreuzplatz Bellevue – Heimplatz (Kunsthaus) – University of Zurich – Universitätsstrasse Zürich Hauptbahnhof – Central – Heimplatz – Hottingerstrasse Central – University of Zurich – Gloriastrasse Löwenplatz – Paradeplatz – Bleicherweg Zürich Hauptbahnhof – Schaffhauserplatz – Hirschwiese – Oerlikon – Schaffhauserstrasse/Binzmühlestrasse Irchel – Hirschwiese – Winterthurerstrasse – Hirschen Schwamendingen – Dübendorferstrasse Schaffhauserplatz – Bucheggplatz – Hofwiesenstrasse

Wherever possible, the cut-and-cover construction method was desirable. Some sections between Central and the university, underneath the Hirschengraben, and from Bellevue to Heimplatz, were to be constructed by drilling and blasting. A direct routing between the main station and Paradeplatz below the middle part of the Bahnhofstrasse was to be avoided due to water mains and cable tunnels. Instead, drilling a slightly curvy alignment along Rennweg and the western side of St. Peterhofstatt was suggested.Das Projekt einer Tiefbahn für Zürich. Schweizerische Bauzeitung 79/47 (1961), S. 851.

All the parties represented in the city parliament supported the project. However, it was rejected in the town referendum with 58,393 to 34,307 votes on 1 April 1962 (63% No). An "unholy alliance" of two groups with completely different motivations was responsible for this outcome. A non-partisan committee had fundamentally spoken against putting the tram below surface and criticized the traffic planners' indignation to restrict motorized private transport. However, a second group, which especially promoted the drivers' needs, demanded the abolition of the tram and requested the construction of an adequate underground network.Hans-Rudolf Galliker: Tramstadt. S. 216. 15 open coaches of type Be 4/4, also known as ‘carps’ and designed for potential use in tunnel sections with high platforms, had been delivered to the VBZ in 1959/60. As a consequence of the underground rejection, no further production series of this type of tramway cars was ordered.

The Underground Project

Planning