suburban train. So for example in Berlin, the mostly underground system is known as the Berlin U-Bahn and it is integrated with the mostly above-ground system, known as the Berlin S-Bahn. The Frankfurt U-Bahn is an important exception, the system being really a light rail transit system with underground sections. Hamburg S-Bahn fulfills all criteria for heavy rail inside the state and city of Hamburg, but some lines go beyond the state border into the state of Niedersachsen and there the S-Bahn runs with lower train frequency. The same applies also to the S-Bahn and U-Bahn in Copenhagen, Denmark, with the only exception that the word "Metro" is used instead of "U-Bahn", and "S-tog" instead of "S-Bahn". (The Danish word "S-tog" applies to the trains (tog), rather than the tracks as in Germany; "S-tog" means "S-train".) Otherwise, the S-Bahn of Berlin and the S-tog of Copenhagen are very similar with the exception of the size. In Switzerland, where there is only one underground railway system in Lausanne, the term metro is generally used, due to the influence from the French language. In Sweden, the metro of Stockholm is called "Tunnelbana" or "T-bana" which refers to the fact that the trains often run in tunnels. The same applies to Norway and the "T-bane" of Oslo. Elevated and overhead Elevated is a shorthand for elevated railway, a railway built on supports over other rights of way, generally city streets. The term overhead tends to be used in Europe. The names of elevated railways are sometimes further abbreviate it to El or L. Some examples include: Chicago "L" The best known elevated transit system in the United States. Vancouver SkyTrain An automated rapid transit system that is mostly elevated. New York City Subway A combination of the old IRT and BMT rapid transit systems that had built or leased numerous elevated lines throughout the entire city. New York "El's" are the oldest ones in the United States, dating from 1869. Today, the majority of "El" lines in New York are in Brooklyn, Queens, and The Bronx. Most "El's" in Manhattan were torn down in the 1940s and 1950s, some replaced by subways. Liverpool Overhead Railway This was the United Kingdom's only true elevated railway, although the London and Greenwich Railway of 1836 was constructed on a brick viaduct for the greater part of its length. SEPTA's Market–Frankford Line is elevated except for the