▁were ▁separated ▁from ▁road ▁traffic ▁and ▁upgrad ed ▁to ▁double ▁track , ▁except ▁for ▁four ▁short ▁sections . ▁In ▁several ▁places ▁wider ▁parallel ▁roads ▁were ▁built ▁next ▁to ▁tram ▁lines . ▁A ▁ped est rian ▁zone ▁was ▁established ▁in ▁the ▁inner ▁city ▁next ▁to ▁the ▁tram ▁lines ▁from ▁ 1 9 7 4 . ▁The ▁only ▁route ▁converted ▁to ▁bus ▁operations ▁was ▁a ▁short ▁line ▁to ▁Be ier the im ▁closed ▁in ▁ 1 9 5 6 . ▁New ▁lines ▁were ▁built ▁from ▁ 1 9 5 3 ▁to ▁close ▁g aps ▁in ▁the ▁network ▁and ▁to ▁connect ▁new ▁neighbourhood s ▁to ▁the ▁tram ▁network . ▁Thus , ▁connections ▁were ▁built ▁to ▁Wald stadt ▁in ▁ 1 9 6 0 , ▁to ▁Nord west stadt ▁in ▁ 1 9 7 5 , ▁to ▁Rhein str ands ied lung ▁in ▁ 1 9 8 0 ▁and ▁to ▁Ober re ut ▁in ▁ 1 9 8 6 . ▁ ▁The ▁rolling ▁stock ▁was ▁renew ed ▁with ▁the ▁proc ure ment ▁of ▁ 2 3 ▁four - ax le ▁tram ▁cars ▁from ▁ 1 9 5 4 ▁and ▁ 7 5 ▁six - and ▁eight - ax le ▁art ic ulated ▁tr ams ▁between ▁ 1 9 5 9 ▁and ▁ 1 9 7 8 , ▁so ▁that ▁the ▁pre - war ▁two - ax le ▁tr ams ▁were ▁with dra wn ▁from ▁the ▁operating ▁fleet ▁by ▁the ▁early ▁ 1 9 7 0 s . ▁New ▁vehicles ▁introduced ▁from ▁ 1 9 6 9 ▁allowed