Al b ▁Valley ▁Transport ▁Company , ▁AV G ) ▁is ▁responsible ▁for ▁the ▁railway ▁infrastr ucture ▁and ▁is ▁the ▁only ▁company ▁operating ▁on ▁the ▁ 1 4 . 4 ▁kilomet re - long ▁line . ▁Origin ally ▁the ▁Bus en bach – It ters bach ▁railway ▁was ▁operated ▁together ▁with ▁the ▁It ters bach ▁to ▁P for z heim ▁line , ▁which ▁later ▁became ▁the ▁P for z heim ▁Light ▁Railway ▁( P for z heimer ▁Klein bahn ). ▁The ▁whole ▁line ▁from ▁Bus en bach ▁to ▁P for z heim ▁was ▁initially ▁built ▁to ▁, ▁later ▁the ▁section ▁from ▁Bus en bach ▁to ▁It ters bach ▁was ▁re built ▁to ▁ ▁and ▁the ▁P for z heim ▁Light ▁Railway ▁was ▁closed . ▁The ▁line ▁has ▁been ▁operated ▁as ▁part ▁of ▁line ▁S ▁ 1 1 ▁of ▁the ▁Kar ls ru he ▁Stadt bahn ▁since ▁ 1 9 9 4 . ▁ ▁History ▁The ▁opening ▁of ▁the ▁Alb ▁Valley ▁Railway ▁from ▁Kar ls ru he ▁to ▁Bus en bach ▁on ▁ 1 4 ▁May ▁ 1 8 9 8 ▁was ▁followed ▁by ▁the ▁opening ▁of ▁the ▁Bus en bach – It ters bach ▁section ▁on ▁ 1 0 ▁April ▁ 1 8 9 9 . ▁These ▁lines ▁were ▁originally ▁met re ▁gauge . ▁The ▁extension ▁to ▁Br öt z ingen , ▁then ▁a ▁sub urb ▁of ▁P for z heim , ▁followed ▁on ▁ 2 ▁January ▁ 1 9 0 0 . ▁The ▁line ▁was ▁initially ▁operated ▁with ▁steam ▁locomot ives . ▁