The S-Bahn is the name of hybrid urban-suburban rail systems serving a metropolitan region predominantly in German-speaking countries. Some of the larger S-Bahn systems provide service similar to rapid transit systems, while smaller ones often resemble commuter or even regional rail systems. The name S-Bahn derives from Schnellbahn (lit. rapid train), Stadtbahn (lit. city train) or Stadtschnellbahn (lit. rapid city train). Similar systems in Austria and Switzerland are known as S-Bahn as well. In Belgium, it is known as S-Trein (Flemish) or Train S (French). In Denmark, they are known as S-tog , and in the Czech Republic as Esko or S-lines. Characteristics There is no complete definition of an S-Bahn system. S-Bahn are, where they exist, the most local type of passenger train service that stops at all existing stations on mainline networks inside and around a city (while other mainline trains only call at major stations). They are slower than regional mainline trains but usually serve as fast crosstown services within the city. The Copenhagen S-tog for example goes up to , faster than most urban heavy rail and mass transit. S-Bahn trains generally serve the hinterland of a certain city, rather than connecting different cities, although in high population density areas a few exceptions to this exist. A good example of such an exception is the Rhine-Ruhr S-Bahn, which interconnects the cities, towns and suburbs of the Ruhr, a large urban agglomeration. Most S-Bahn 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 and lines can be purpose-built S-Bahn lines. S-Bahn trains typically use overhead lines or a third rail for traction power. In Hamburg both methods are used, depending on which line is powered. In smaller S-Bahn systems and suburban sections of larger ones, trains typically share tracks with other rail traffic, with the Berlin S-Bahn, Hamburg S-Bahn and Copenhagen S-train being notable exceptions. Busy S-Bahn corridors sometimes have sections of exclusive trackage of their own but parallel to mainline railways. Many of the larger S-Bahn systems will also have central corridors of exclusive trackage that individual suburban branches feed into, creating a high frequency trunk corridor. In many cases, the central corridor is a dedicated underground line in the city centre with close stop spacing and a high frequency, similar to metro systems, created