▁conduct or - less ▁operation ▁and ▁thus ▁made ▁further ▁rational isation ▁of ▁operations ▁possible . ▁ ▁The ▁ac quisition ▁of ▁the ▁Alb ▁Valley ▁Railway ▁and ▁the ▁Bus en bach - It ters bach ▁railway ▁along ▁with ▁the ▁Al bt al - Ver kehr s - G es ellschaft ▁( Al b ▁Valley ▁Transport ▁Company , ▁AV G ) ▁in ▁ 1 9 5 7 ▁and ▁their ▁reg aug ing ▁and ▁connection ▁to ▁the ▁tram way ▁network ▁allowed ▁AV G ▁vehicles ▁to ▁operate ▁on ▁the ▁tracks ▁of ▁Verkehr s bet rie be ▁Kar ls ru he , ▁giving ▁direct ▁services ▁between ▁the ▁surrounding ▁coun tr ys ide ▁and ▁central ▁Kar ls ru he . ▁Further ▁enh anc ements ▁in ▁the ▁region ▁came ▁after ▁ 1 9 7 9 ▁with ▁the ▁integration ▁of ▁the ▁Hard t ▁Railway ▁in ▁the ▁AV G ▁and ▁the ▁development ▁of ▁the ▁Kar ls ru he ▁model ▁of ▁tram - train ▁operations . ▁In ▁ 1 9 9 4 , ▁a ▁common ▁fare ▁system ▁was ▁introduced ▁with ▁the ▁establishment ▁of ▁the ▁Kar ls ru her ▁Verkehr s ver bund ▁( Kar ls ru he ▁Transport ▁Association , ▁K V V ). ▁In ▁ 1 9 9 7 , ▁Verkehr s bet rie be ▁Kar ls ru he ▁was ▁converted ▁into ▁a ▁public ▁company , ▁previously ▁it ▁had ▁been ▁a ▁public ▁utility ▁owned ▁by ▁the ▁city . ▁ ▁Despite ▁the ▁extensive ▁modern isation , ▁passenger ▁numbers ▁st agn ated ▁between ▁ 1 9 5 0 ▁and ▁ 1 9 8 5 ▁at