Starting in the 1970s, regional rail around major cities has been transformed into high-frequent S-Bahn networks, currently the following systems exist (partly) in Baden-Württemberg: Stuttgart S-Bahn, Rhine-Neckar S-Bahn, Breisgau S-Bahn and Basel S-Bahn. In and around the cities of Karlsruhe and Heilbronn, the Karlsruhe Stadtbahn system combines elements of traditional S-Bahns with tram operations within the urban cores (tram-trains).
sTARtiNG iN thE 1970s, rEGioNAL raIL ArounD majOr citiES Has beeN trANsFormeD into high-fREqUent s-BAhn netwoRkS, curRently ThE FolloWinG systEmS exisT (partLY) in BAdEn-württeMbeRG: stutTgaRt s-bahN, rHInE-NEckAr s-BaHn, breiSGau s-Bahn ANd Basel s-bahN. in And ArOunD The cItiEs oF KARLsrUhE aND hEiLBRonn, thE kArlsRUHE sTAdtbaHN syStem cOmbines elementS Of tradITionAl s-baHNS with tRaM oPerAtions WIThIn The urBAn CORes (tram-tRaINs).