2 0 1 1 , ▁the ▁technology ▁has ▁been ▁used ▁as ▁part ▁of ▁other ▁systems ▁around ▁the ▁world , ▁with ▁Re ims ▁Tr am way , ▁Rio ▁de ▁Janeiro ▁V LT , ▁Ang ers ▁tram way ▁and ▁Dub ai ▁Tr am ▁all ▁having ▁adopted ▁the ▁technology . ▁ ▁Technology ▁Gr ound - level ▁power ▁supply ▁is ▁used , ▁primarily ▁for ▁a est h etic ▁reasons , ▁as ▁an ▁alternative ▁to ▁overhead ▁lines . ▁It ▁is ▁different ▁from ▁the ▁condu it ▁current ▁collection ▁system ▁( which ▁was ▁one ▁of ▁the ▁first ▁ways ▁of ▁supp lying ▁power ▁to ▁a ▁tram ▁system ) ▁as ▁it ▁involves ▁b ury ing ▁a ▁third ▁and ▁fourth ▁rail ▁in ▁an ▁under ground ▁condu it ▁( ‘ v ault ’ ) ▁between ▁the ▁running ▁rails . ▁Con du it ▁current ▁collection ▁was ▁used ▁in ▁historic ▁tram ▁systems ▁in ▁Washington , ▁Manh attan , ▁Paris , ▁Berlin , ▁Marse illes , ▁Vienna , ▁Budapest ▁and ▁London . ▁It ▁fell ▁into ▁dis use ▁because ▁overhead ▁w ires ▁proved ▁much ▁less ▁expensive ▁and ▁troubles ome ▁for ▁street ▁rail ways ▁and ▁because ▁in ▁Manh attan , ▁Paris , ▁Washington ▁and ▁West ▁Berlin , ▁all ▁tr ams ▁were ▁replaced ▁by ▁bus es ▁for ▁reasons ▁un related ▁to ▁the ▁power ▁supply ▁issue . ▁In ▁Prag ue ▁on ▁the ▁Charles ▁Bridge ▁( Kar l ů v ▁most ), ▁a ▁system ▁invent ed ▁by ▁Fr anti š ek ▁K ři ží k ▁was ▁used , ▁similar ▁to ▁today ' s ▁A PS . ▁ ▁Un like ▁the ▁track -