Rhine-Ruhr Stadtbahn
The Rhine-Ruhr Stadtbahn is an umbrella system of all of the Stadtbahn ( light rail ) lines included in the integrated public transport network of Verkehrsverbund Rhein-Ruhr ( VRR ) which covers the Rhine-Ruhr metropolitan area in western Germany . 
<triplet> Rhine-Ruhr Stadtbahn <subj> Verkehrsverbund Rhein-Ruhr <obj> part of <triplet> Rhine-Ruhr metropolitan area <subj> Germany <obj> country