 The KVB and SWB are members of the Verkehrsverbund Rhein-Sieg (VRS – Rhein-Sieg Transit Authority), formed in 1987 to consolidate the transit authorities in the metropolitan Cologne area and operate a joint fare structure.There were 38 underground stations, with an additional four being added since 2015.The Cologne Stadtbahn traces its history to the first horsecar lines that started operating in 1877.