▁to ▁the ▁Deutsche ▁Bahn ▁network ▁with ▁several ▁stations , ▁including ▁its ▁main ▁station , ▁K ref eld ▁Haupt bahn hof . ▁They ▁are ▁served ▁by ▁Inter city , ▁Regional - Express ▁and ▁Regional bahn ▁trains . ▁The ▁Düsseldorf - based ▁Rhein bahn ▁oper ates ▁a ▁Stadt bahn ▁service ▁to ▁the ▁cent r ally ▁located ▁R he inst ra ße ▁stop . ▁This ▁line ▁was ▁the ▁first ▁electric ▁inter - city ▁rail ▁line ▁in ▁Europe , ▁established ▁in ▁ 1 8 9 8 , ▁and ▁commonly ▁called ▁the ▁K - B ahn ▁because ▁of ▁the ▁letter ▁" K " ▁used ▁to ▁denote ▁the ▁trains ▁to ▁K ref eld . ▁Now ad ays , ▁in ▁the ▁V R R ▁notation , ▁it ▁is ▁called ▁U 7 6 , ▁with ▁the ▁morning ▁and ▁afternoon ▁express ▁trains ▁number ed ▁as ▁U 7 0 , ▁the ▁line ▁number ▁there ▁col oured ▁red ▁instead ▁of ▁the ▁usual ▁blue ▁used ▁for ▁U - B ahn ▁lines . ▁The ▁term ▁K - B ahn , ▁however , ▁prev ails ▁in ▁common ▁usage . ▁ ▁The ▁city ▁of ▁K ref eld ▁itself ▁oper ates ▁four ▁tram way ▁and ▁several ▁bus ▁lines ▁under ▁the ▁um bre lla ▁of ▁SW K ▁M OB IL , ▁a ▁city - owned ▁company . ▁Since ▁ 2 0 1 0 , ▁ 1 9 ▁of ▁the ▁oldest ▁tr ams ▁of ▁the ▁type ▁D UE W AG ▁GT 8 ▁were ▁replaced ▁by ▁modern ▁bar rier - free ▁tr ams ▁of ▁the ▁type ▁Bomb ard ier ▁F lex ity