9 6 , ▁a ▁modified ▁plan ▁was ▁confirmed ▁at ▁a ▁further ▁refer endum ▁in ▁ 2 0 0 2 . ▁At ▁the ▁end ▁of ▁ 2 0 0 5 ▁the ▁so - called ▁" comb ined ▁solution " ▁( K omb il ös ung ) ▁for ▁the ▁Stadt bahn ▁tunnel ▁completed ▁the ▁planning ▁appro val ▁process . ▁In ▁December ▁ 2 0 0 8 , ▁the ▁Kar ls ru he ▁regional ▁council ▁approved ▁the ▁details ▁of ▁the ▁work . ▁ ▁The ▁Stadt bahn ▁tunnel ▁has ▁been ▁under ▁construction ▁since ▁ 2 0 1 0 . ▁ ▁The ▁project ▁consists ▁of ▁several ▁parts : ▁The ▁construction ▁of ▁a ▁two - track ▁rail ▁tunnel ▁in ▁the ▁east - west ▁direction ▁in ▁Kriegs straße ▁between ▁Dur la cher ▁Tor ▁and ▁M ühl burger ▁Tor ▁with ▁a ▁branch ▁from ▁Mark t platz ▁to ▁the ▁south ▁to ▁the ▁convention ▁centre ▁( K ong ress zent rum ▁Kar ls ru he ; ▁about ▁ 3 . 5   km ▁of ▁tunnel ▁with ▁seven ▁stops ); ▁The ▁construction ▁of ▁a ▁two - track ▁tram ▁line ▁in ▁Kriegs straße ▁between ▁Karl stor ▁and ▁M end els so hn platz , ▁about ▁ 4 0 0 ▁metres ▁south ▁of ▁Kaiser straße ▁( length : ▁ 1 . 2   km ) ▁The ▁construction ▁of ▁a ▁road ▁tunnel ▁under ▁Kriegs straße ; ▁The ▁dis m ant ling ▁of ▁the ▁surface ▁tram ▁tracks ▁in ▁Kaiser straße ▁between ▁Europ ap l atz ▁and ▁K ron en platz ▁and ▁in ▁Karl - F ried rich -