- 2 5 ▁t rol ley b uses ▁were ▁sold ▁to ▁the ▁ ▁in ▁Bos nia - Her z egov ina . ▁ ▁Current ▁fleet ▁ ▁A ▁total ▁of ▁ 2 5 ▁t rol ley b uses ▁are ▁currently ▁available ▁for ▁use ▁on ▁the ▁St . ▁G allen ▁system ; ▁a ▁maximum ▁of ▁ 2 1 ▁are ▁required ▁simultaneously . ▁The ▁present ▁fleet ▁compr ises ▁ 1 7 ▁art ic ulated ▁bus es ▁and ▁eight ▁bi - art ic ulated ▁bus es , ▁all ▁of ▁which ▁are ▁of ▁low - floor ▁design : ▁ ▁Fle et ▁no . ▁ 1 5 5 , ▁which ▁was ▁originally ▁a ▁single - art ic ulated , ▁high - floor ▁t rol ley bus , ▁is ▁an ▁exception al ▁vehicle . ▁ ▁Four teen ▁years ▁after ▁its ▁entry ▁into ▁service , ▁it ▁was ▁length ened ▁into ▁a ▁bi - art ic ulated ▁vehicle , ▁by ▁the ▁addition ▁of ▁a ▁second , ▁low - floor , ▁trailing ▁segment . ▁Sim ult ane ously , ▁its ▁design ation ▁was ▁changed ▁from ▁B GT ▁ 5 - 2 5 ▁to ▁B G GT ▁ 5 - 2 5 . ▁ ▁Origin ally ▁it ▁was ▁planned ▁to ▁carry ▁out ▁a ▁similar ▁conversion ▁to ▁eight ▁or ▁nine ▁other ▁vehicles ▁of ▁this ▁type . ▁ ▁However , ▁due ▁to ▁technical ▁problems ▁with ▁the ▁prototype , ▁it ▁was ▁decided ▁instead ▁to ▁purchase ▁the ▁seven ▁brand - new ▁bi - art ic ulated ▁t rol ley b uses , ▁nos . ▁ 1 8 8