Stuttgart is the capital of the German Bundesland Baden-Württemberg and has 550, 000 inhabitants, with Stuttgarter Straßenbahnen AG serving an area where almost 900, 000 people live. The city is spread out over several hills with the city centre in the valley. Therefore metro lines are classified as:
1) running along the main valley: U1, U14, U2
The Stuttgart Stadtbahn is not a real metro, but a light rail system that's largely underground in the city centre, and which runs at grade with level crossings, though on a separate right-of-way, in other areas. Between 1966 and 1970 the first tunnel opened in the city centre along route U1 (Charlottenplatz - Marienplatz). Subsequently and until 1983 all city tunnels were completed. In the beginning all tunnels were used by existing tram lines (similar to the Brussels pré-métro), but in 1985 new Stadtbahn trains of the DT8 type started operating on the 8.1 km long route U3 in the south of the city between Plieningen and Vaihingen.
The Stuttgart Stadtbahn uses standard European gauge (1435 mm), whereas the former tram system was narrow gauge (1000 mm). Along some routes therefore 3-rail tracks can still be seen, as well as some lower platform sections, which have become obsolete once line 15 had been upgraded to Stadtbahn operation. Some routes (e.g. the panoramic route from Olgaeck to Ruhbank) will remain 3-track to allow special rides with heritage tramway vehicles.
Apart from the city tunnels, there are major tunnel sections on route U6 through Feuerbach in the north, and along route U5/U6 between Bopser and Degerloch. From this tunnel a southbound branch opened in May 1998, which is part of U7 to Heumaden and Ostfildern.
The last metre-gauge line 15 was closed down on 8 Dec 2007, with the central and southern parts starting Stadtbahn operation the following day. For the northern section between Zuffenhausen and Stammheim an approx. 1 km tunnel was built (including Kirchtalstraße underground station) through the Zuffenhausen town centre and to pass under the mainline tracks. The rest of the route to Stammheim was upgraded to Stadtbahn operation, with some on-street running remaining with the Stammheim district. The northern U15 reopened in Dec. 2011.
A special line in the Stuttgart rail network is line 10, a rack railway between Marienplatz (U1/14) and Degerloch (U5/6). This train has a special bicycle car so bikers don't have to climb up the steep hill.
Like in other German cities, the S-Bahn operated by DB (Deutsche Bahn) is an important means of transport also within the city (about 20 stations within the city limits).
U14 - U5* U6* -
* On 12 Dec 2010 the northern legs of lines U5 and U7 were switched, as were the western legs of U2 and U4. At the same time, a new line U12 was introduced, while line U6 was withdrawn from the section Vaihinger Straße - Vaihingen.
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