of system. Other Definitions of Subway Bus subways are uncommon but do exist, though in these cases the non-underground portions of route are not called subways. Until March 2019, Seattle, Washington had a bus subway downtown in which diesel-electric hybrid buses and light rail trains operated in a shared tunnel. The hybrid buses ran in electrical-only mode while traveling through the tunnel and overhead wires power the light rail trains which continue to operate in the tunnel. Bus subways are sometimes built to provide an exclusive right-of-way for bus rapid transit lines, such as the MBTA Silver Line in Boston. Subway, outside the US, and especially in Europe, often refers to an underground pedestrian passageway linking large road interconnections that are often too difficult or dangerous to cross at ground level. In Canada, the term subway may be used in either sense. Underground and tube The usage of underground is very similar to that of subway, describing an underground train system. In London the colloquial term tube now refers to the London Underground, and is the most common word used for the underground system; and it is used by Transport for London the local government body responsible for most aspects of the transport system throughout Greater London. However, strictly speaking, it should only refer to those deep lines which run in bored circular tunnels as opposed to those constructed near to the surface by 'cut-and-cover' methods. The Glasgow metro system is known as the Glasgow Subway or colloquial as "the subway". The word metro is not usually used in London or Glasgow to refer to those cities' metros, but it is used in and around Newcastle upon Tyne to refer to the Tyne and Wear Metro. Overground In the UK, the term overground was created in 2007 by Transport for London to refer to a mainly above-ground suburban rail network serving Greater London, the London Overground, which took over Silverlink Metro routes. Confusingly, the term overground is also used to refer to National Rail networks within London generally, or any non-London Underground rail service in everyday speech U-Bahn and S-Bahn The term metro is not usually used to describe metro systems in German-speaking areas (Germany, Austria and parts of Switzerland), instead using the term U-Bahn—a shortening of Untergrundbahn, meaning "underground railway"—and S-Bahn—an abbreviation for the German "Stadtschnellbahn" or just "Schnellbahn" (fast city train, fast train) the more common English translation,