▁cross ▁the ▁Rh ine ▁brid ges ▁between ▁the ▁two ▁cities ▁and ▁one ▁other ▁line ▁( 1 0 ) ▁runs ▁through ▁Ludwig sh afen ▁only . ▁In ▁late ▁ 2 0 0 8 ▁Line ▁ 4 ▁was ▁extended ▁and ▁replaced ▁Line ▁ 1 4 ▁( also ▁known ▁as ▁" R hein - Ha ard t - B ahn "). ▁Line ▁ 4 ▁now ▁serves ▁as ▁a ▁long - distance ▁line , ▁which ▁runs ▁from ▁Bad ▁D ür k heim ▁to ▁Ludwig sh afen , ▁Mann heim ▁and ▁Hed des heim . ▁The ▁bus ▁network ▁consists ▁of ▁about ▁ten ▁municipal ▁lines ▁and ▁further ▁regional ▁lines . ▁ ▁A ▁rather ▁strange ▁feature ▁of ▁Ludwig sh afen ' s ▁public ▁transport ▁system ▁is ▁the ▁existence ▁of ▁four ▁under ground ▁tram ▁stations ▁( R ath aus , ▁Dan z iger ▁Platz ▁( closed ▁since ▁late ▁ 2 0 0 8 ), ▁Haupt bahn hof , ▁Hem sh of straße ). ▁They ▁go ▁back ▁to ▁the ▁ 1 9 7 0 s , ▁when ▁a ▁common ▁under ground ▁network ▁in ▁Mann heim ▁and ▁Ludwig sh afen ▁was ▁planned . ▁The ▁r ash ▁construction ▁of ▁these ▁first ▁stations ▁in ▁Ludwig sh afen ▁became ▁super fl uous ▁when ▁Mann heim ▁cancel led ▁the ▁project ▁due ▁to ▁its ▁enorm ous ▁costs . ▁ ▁Region ▁and ▁neighb ours ▁ ▁The ▁tw in ▁cities ▁of ▁Mann heim ▁and ▁Ludwig sh afen ▁closely ▁co oper ate ▁in ▁many ▁areas ; ▁although ▁they ▁are ▁separated ▁by ▁the ▁Baden - W ür ttemberg / R hin eland