The Copenhagen S-train (), the S-train of Copenhagen, Denmark is a key part of public transport in the city. It is a hybrid urban-suburban rail serving most of the Copenhagen urban area, and is analogous to S-Bahn systems of Berlin, Vienna and Hamburg. The trains connect the Copenhagen inner city with Hillerød, Klampenborg, Frederikssund, Farum, Høje Taastrup and Køge. There are 170 km of double track with 86 S-train stations, of which eight are in neighbouring towns outside greater Copenhagen. The S-train is run by DSB S-tog A/S while Banedanmark owns the tracks and signals. Rail services are operated by "Fourth Generation" S-trains divided into 104 8-car train sets (Class SA) and 31 4-car train sets (Class SE). The system operates in tandem with the separately owned Copenhagen Metro which operates in the city centre, Frederiksberg and Amager. The two systems carry 500,000 passengers daily with S-tog serving more than 357,000 passengers a day. S-tog is complemented by regional trains, local diesel-powered trains within Metropolitan Copenhagen, an extensive bus network and two lines of shuttle boats called harbour buses. The city's bus terminals are often adjacent to an S-train or Metro station. The different networks use a common system for fare zones and tickets. History The lines used by the Copenhagen S-Train suburban rail system in Denmark are six radial and two connecting, rail lines built during the late 19th and early 20th centuries as commuter transport to and from the residential areas around the city centre. The S-line aimed to electrify the existing local rail network around Copenhagen. Preparations for the decision were made in the Electrification Commission of 1926, following several other approaches to plans. The Commission presented a report in 1929, in which it proposed that short-distance lines from Copenhagen to Klampenborg, as well as possibly Frederiksberg-Vanløse-Hellerup, should be electrified first – then the line to Holte, when the double track Holte-Hillerød was taken into use for the ordinary trains. After consideration of the proposal by DSB, the section to Valby was added as the first stage for electrification of the section to Ballerup, and a bill was submitted and adopted in April 1930. The first section opened on 3 April 1934, and ran from Klampenborg to Hellerup and Vanløse to Frederiksberg. It was the first electrically powered railway in Denmark. Stations were marked from the beginning with an "S" similar to those in Berlin S train