After years of debate, a referendum of Zürich Canton agreed, on 29 November 1981, to the borrowing of CHF 520 million for the construction of the main lines for the Zürich S-Bahn, based around a tunnel from the Zürich main station (connecting to the west, south and north) to Zürich Stadelhofen station (connecting to the southeast) and Dietlikon (connecting to the northeast) and Dübendorf (connecting to the east). On 27 May 1990, the S-Bahn was put into operation and then expanded in several phases into the current 380 kilometre long network.