The Zürich–Baden railway line is a major railway line in Switzerland connecting the cities of Zürich and Baden. It forms part of the major east-west route between Zürich and Olten. The line generally follows the south bank of the Limmat from Zürich to Baden. A new line, the Heitersberg line, opened in 1975, branches off in Killwangen-Spreitenbach and follows a more southerly route through the Heitersberg Tunnel towards Olten. The Zürich–Baden railway is electrified at 15 kV 16.7 Hz and much of it has four tracks. The section between Zürich and Baden was opened in 1847 and was the first line opened in Switzerland, apart from a line from Mulhouse, France to Basel. The line was extended from Baden to Olten in 1858. History The line between Zürich and Baden was opened on 7 August 1847 by the Swiss Northern Railway (, SNB). It was the first line built in Switzerland, except for the line built from Mulhouse to Basel by the French company, Strasbourg–Basel Railway (), opened to a temporary station outside Basel's walls on 15 June 1844 and to the permanent station on 11 December 1845. The construction of railways in Switzerland was delayed compared to most of its neighbours, partly as a result of its mountainous geography. In 1837, the Zürich Chamber of Commerce commissioned the engineer Alois Negrelli to investigate the route of such a line. In October of the same year the Zürich-Basel railway company was founded. The chosen route would lead from Zürich to Würenlos via Dietikon along the south bank of the Limmat, then cross the river to follow the north bank of the Limmat follow Wettingen, Ennetbaden and Obersiggenthal. In Untersiggenthal the line would turn to the north and have crossed the Aare at Döttingen. It would have then followed the south bank of the Rhine to Basel. In April 1838 surveying of the route began, but angry residents obstructed their work. The Züriputsch of 1839 and a civil war-like Constitutional dispute in the canton of Aargau further delayed the start of construction. Although the Aargau parliament passed a law permitting compulsory purchase in November 1840, several shareholders lost their financial guarantees, and the company had to be dissolved in December 1841. In May 1845 a new committee was formed under the leadership of the Zürich industrialist Martin Escher. The planned line would now keep to the south bank of the Limmat,