Vestische Straßenbahnen

The Verkehrsverbund Rhein-Ruhr (abbreviated VRR) is the public transport association covering the area of the Rhine-Ruhr conurbation in Germany. It was founded on 1 January 1980, and is Europe’s largest body of such kind, covering an area of some 5,000 km² with more than seven million inhabitants, spanning as far as Dorsten in the north, Dortmund in the east, Langenfeld in the south, and Mönchengladbach and the Dutch border in the west.

In 2004, roughly 1 billion trips were made by way of the VRR network.

With the introduction of the VRR in 1980 a new line numbering systems for all bus, tram and Stadtbahn lines in the VRR area was introduced. The VRR was dividied into ten sections getting a key number (e.g. 4 for Dortmund), the first number in the three-digit line numbers represents these key numbers. The last two numbers are the actual identifying numbers. These are the key numbers:

Stadtbahn lines are identified with the prefix "U" followed by the key number and a one-digit identifying. The key numbers 2, 5, 8, 9 and 0 are not used for Stadtbahn lines, but the Düsseldorf Stadtbahn is planning is approaching 10 lines in 2016, all new lines afterwards will get the 8 key number. The Wuppertal Schwebebahn is officially called line 60, but because it does not run underground, the U prefix is not used.

After the integration of the Niederrhein area north of Duisburg, a new section for key numbers was introduced; the buses have a one- or two-digit number with no key number for identification.

There are several exceptions of that system, also, there some extra line numbers e.g. for express buses:

As of 2012^[update], the VRR network consists of 978 lines, of which there are:

Additionally, the VRR tariff is recognized on the following lines outside the VRR area:

...
Wikipedia