The Glattalbahn, originally known as the Stadtbahn Glattal, was a project that was ultimately successful in introducing a modern rapid-transit system to the Glattal area of Switzerland, to the north of the city of Zürich. Stadtbahn Glattal was developed as a metre gauge tram system with through-running to neighbouring Zürich. It was built and is owned by the Verkehrsbetriebe Glattal (VBG), but is operated under contract to them by the Verkehrsbetriebe Zürich (VBZ). Stadtbahn Glattal is the official denomination of this system. This name is used in all official and legal processes. Elsewhere, the alternative term, Glattalbahn, is frequently substituted. The latter term correctly refers to the railway line from Wallisellen to Uster. It is, however, widely used for the Stadtbahn Glattal system and is prominent on the official website and advertising material. Stadtbahn Glattal is sometimes described in German as a Mittelverteiler, i.e., intermediate distributor (intermediate between S-Bahn and bus). History Pre-existing situation A private tramway company, the Strassenbahn Zürich-Oerlikon-Seebach (ZOS), opened a line from Zürich Seebach to Glattbrugg in 1908. At the time, this area was sparsely inhabited and the line was not a commercial success. The link was replaced by a bus service in 1931. In the period following World War II, the Glattal area experienced a rapid boom as population and industry spilled over from nearby Zürich. The development was accelerated by the inauguration of Zurich Airport near Kloten in 1953. The economic growth of the Glattal region is continuing to this day. One of the consequences of the rapid transformation is rising traffic congestion. The area was, and still is, served by the Zürich S-Bahn, which provides frequent and fast connections between its stations. There are also fast train connections from Zurich Airport to central Zürich, some calling in Oerlikon. However the stations of the S-Bahn are widely spaced and, prior to the development of the Stadtbahn Glattal, onward distribution from the railway stations depended on bus services. Investigation By the 1990s, it was recognised that the bus services in the Glattal region were suffering from both road congestion and vehicle overloading. It was decided to investigate the construction of a rapid transit system. Following the evaluation of alternatives, including a monorail system, a metre gauge tram was selected on account of its compatibility with that of neighbouring Zürich and the ability to provide through services. Development The regional bus operating authority for the Glattal