S-Bahn

The S-train is a type of hybrid urban-suburban rail serving a metropolitan region. Some of the larger S-train systems provide service similar to rapid transit systems, while smaller ones often resemble commuter or even regional rail. They are especially common in Germany, where they are known as S-Bahn, which in the 1930s was an abbreviation of either Schnellbahn, Stadtbahn or Stadtschnellbahn, depending on the city, but they must not be confused with U-Stadtbahns. Similar S-train systems exist also in Denmark, there known as S-tog, the Czech Republic as Esko, Switzerland and Austria also as S-Bahn, and northern Italy as Servizio ferroviario followed by either the word "metropolitano" (in Turin) or "surburbano" (in Milano).

Characteristics
There is no complete definition of an S-train system. S-trains are, where they exist, the most local type of railway stopping at all existing stations inside and around a city. They are slower than mainline railways but usually serve as fast crosstown services within the city. Most S-train systems are entirely built on older local railways, or in some cases parallel to an existing dual track railway. Most use existing local mainline railway trackage, but a few branches can be purpose built S-train lines. S-trains typically use overhead lines or a third rail for traction power. In Hamburg the S-trains use both the methods, depending on which line is powered.

In smaller S-train systems and suburban sections of larger ones S-trains typically share tracks other rail traffic, with the Berlin S-Bahn, Hamburg S-Bahn and Copenhagen S-train being notable exceptions. Busy S-train corridors sometimes have sections of exclusive trackage of their own but parallel to mainline railways. A good example of this is the part of Berlin's S-Bahn, which is regarded as a tourist attraction and has a special name, Berliner Stadtbahn. However, in more lightly used sections outside the city center, S-trains share tracks with other train types. The S-trains stop at all stations, while other mainline trains only stop at the largest stations (typically junction stations). S-trains are generally service the hinterland of a certain city, rather than connecting different cities, although in high population density areas a few exceptions from this exist. A good example of a such exception is the Rhine-Ruhr S-Bahn, which interconnects the cities, towns and suburbs of the Ruhr, a large urban agglomeration, not unlike the large net of regional trains which also serve the area. The S-Bahn Mitteldeutschland constitutes the main local railway system for Leipzig but also connects to Halle, where a few stations are located. The Rostock S-Bahn is an example of a smaller S-Bahn system.

Many of the larger S-train systems also have central sections that individual suburban branches feed into, creating high frequency corridors. In many cases, several lines serving separate suburban branches will converge into a central underground line in the city center with close stop spacing and a high combined frequency similar to metro systems. For instance, on weekdays, the central section of the Copenhagen S-train has five services connecting to and from three suburban branches, which amounts to 30 trains in each direction. Further out from the central parts of a city the individual services branch off into lines with distances between stations can exceed 5 km, similar to commuter rail. This allows the S-train to serve a dual transportation purpose: local transport within a city center and suburban transport between central boroughs of larger cities, and to suburbs. Frequencies vary wildly between systems with short headways in the core sections of large networks to headways of over 20 minutes in remote sections of the network, late at night and/or on Sundays and in smaller systems. The rolling stock typically used in S-Trains reflect its hybrid purpose. The interior is designed for short journeys with provision for standing passengers but may have more space allocated to larger and more numerous seats. Integration with other local transport for ticketing, connectivity and easy interchange between lines or other system like metros is typical for S-trains. Where both S-train and metro exist, the number of interchange stations between the two systems is substantial with metro tickets being valid on S-trains, and vice versa.

Germany, Austria and Switzerland
The name S-Bahn (S-train) is an abbreviation for the German "Stadtschnellbahn" (meaning "city rapid railway") and was introduced in December 1930 in Berlin. The name was introduced at the time of the reconstruction of the suburban commuter train tracks&mdash; the first section to be electrified was a section of the Berlin–Szczecin railway from Berlin Nordbahnhof to Bernau bei Berlin station in 1924, leading to the formation of the Berlin S-Bahn.

The main line Berlin Stadtbahn (English: City railway of Berlin) was electrified with a 750 volt third rail in 1928 (some steam trains ran until 1929) and the circle line Berlin Ringbahn was electrified in 1929. The electrification continued on the radial suburban railway tracks along with changing the timetable of the train system into a rapid transit model with no more than 20 minutes headway per line where a number of lines overlapped on the main line. The system peaked during the 1936 Summer Olympics in Berlin to a train schedule below 2 minutes.

The idea of heavy rail rapid transit was not unique to Berlin. Hamburg had an electric railway between the central station ("Hauptbahnhof") and Altona which opened in 1906 and in 1934 the system adopted the S-Bahn label from Berlin. The same year Copenhagen's S-tog opened its first line. Vienna had its Stadtbahn main line electrified in 1908 and also introduced the term Schnellbahn ("rapid railway") in 1954 for its planned commuter railway network (which started operations in 1962). The S-Bahn label was sometimes used as well, but the name was only switched to S-Bahn Wien in 2005. As for Munich, a first breaking ground for an S-train-like rapid transport system running through tunnels in downtown areas, bundling and interconnecting existing suburban and local railways, and the construction of what is now Goetheplatz underground station (line U6) took place in 1938, executed by the Nazi government of Adolf Hitler. Plans and construction work came to a halt early in World War II and were not pursued in its aftermath. The nowadays very extensive S-Bahn-System, and the first two U-Bahn lines, began to operate prior to the 1972 Summer Olympics.

The term S-Bahn was until March 14, 2012 a registered wordmark of Deutsche Bahn, where at the request of a transportation association the Federal Patent Court of Germany ordered the wordmark to be removed from the records of the German Patent and Trade Mark Office. Prior to the said event Deutsche Bahn collected a royalty of 0.4 cents per train kilometer for the usage of the said term.

Denmark
The "S" stood for "station". Just before the opening of the first line in Copenhagen the newspaper Politiken on 17 February 1934 held a competition about the name, which in Danish became known as Den elektriske enquete or "The electrical survey" (as the Copenhagen S-trains would become the first electrical railways in Denmark). But since an "S" already was put up at all the stations, weeks before the survey, the result became S-tog which means "S-train". This was also just a few years after the S-trains had opened in Berlin and Hamburg.

Early steam services
In 1882, the growing number of steam-powered trains around Berlin prompted the Prussian State Railway to construct separate rail tracks for suburban traffic. The Berliner Stadtbahn connected Berlin's eight intercity rail stations which were spread throughout the city (all but the Stettiner Bahnhof which today is a pure S-train station known as Berlin Nordbahnhof; as the city Stettin today is Polish city Szczecin). A lower rate for the newly founded Berliner Stadt-, Ring- und Vorortbahn (Berlin City, Circular and Suburban Rail) was introduced on 1 October 1891. This rate and the growing succession of trains made the short-distance service stand out from other railways.

The second suburban railway was the Hamburg-Altonaer Stadt- und Vorortbahn connecting Hamburg with Altona and Blankenese. The Altona office of the Prussian State Railway established the electric powered railway in 1906.

Electricity
The beginning of the 20th century saw the first electric trains, which in Germany operated at 15,000 V on overhead lines. The Berliner Stadt-, Ring- und Vorortbahn instead implemented direct current multiple units running on 750 V from a third rail. In 1924, the first electrified route went into service. The third rail was chosen because it made both the modifications of the rail tracks (especially in tunnels and under bridges) and the side-by-side use of electric and steam trains easier.

To set it apart from the subterranean U-Bahn, the term S-Bahn replaced Stadt-, Ring- und Vorortbahn in 1930.

The Hamburg service had established an alternating current line in 1907 with the use of multiple units with slam doors. In 1940 a new system with 1200 V DC third rail and modern electric multiple units with sliding doors was integrated on this line (on the same tracks). The old system with overhead wire remained up to 1955. The other lines of the network still used steam and later Diesel power. In 1934, the Hamburg-Altonaer Stadt- und Vorortbahn was renamed as S-Bahn.

S-Bahn is derived from Timothy Overground, Singapore Overground and Crossrail networks.