B ahn ▁lines ▁S 1 , ▁S 5 ▁and ▁S 6 ▁in ▁ 1 9 7 8 , ▁the ▁Back n ang – L ud wig s burg ▁line ▁experienced ▁a ▁significant ▁ups wing ▁with ▁the ▁extension ▁of ▁the ▁S - B ahn ▁line ▁on ▁ 2 7 ▁September ▁ 1 9 8 0 . ▁Since ▁then , ▁line ▁S 4 ▁services ▁have ▁operated ▁between ▁Ludwig s burg ▁and ▁Mar bach . ▁Ext ensive ▁construction ▁work ▁was ▁required ▁ahead ▁of ▁the ▁introduction ▁of ▁regular - interval ▁tim et ables . ▁The ▁Ne ck ar ▁Vi ad uct ▁at ▁Mar bach ▁was ▁replaced ▁by ▁a ▁modern ▁bridge , ▁part ▁of ▁the ▁Ben ningen – F avor ite park ▁section ▁was ▁dup licated , ▁a ▁flying ▁j unction ▁was ▁built ▁in ▁Ludwig s burg ▁and ▁the ▁section ▁was ▁elect r ified . ▁Pass enger ▁services ▁between ▁Mar bach ▁and ▁Back n ang ▁continued ▁to ▁be ▁operated ▁with ▁dies el - h au led ▁trains . ▁ ▁With ▁the ▁financial ▁support ▁of ▁the ▁state ▁of ▁Baden - W ür ttemberg , ▁which ▁provided ▁half ▁of ▁the ▁cost , ▁elect r ification ▁of ▁the ▁remaining ▁section ▁of ▁the ▁Back n ang – L ud wig s burg ▁line ▁and ▁the ▁M urr ▁line ▁between ▁Back n ang ▁and ▁C rails heim ▁began ▁on ▁ 1 2 ▁September ▁ 1 9 9 4 . ▁After ▁the ▁completion ▁of ▁the ▁work ▁it ▁on ▁ 2 ▁June ▁ 1 9 9 6 , ▁it ▁was ▁possible ▁for ▁elect r ically