Line 4 , currently known as Trinitat Nova â `` La Pau , usually called `` lÃ nia groga '' ( yellow line ) , is a line in the Barcelona Metro network operated by TMB . â '' Line 4 , currently known as Trinitat Nova â `` La Pau , usually called `` lÃ nia groga '' ( yellow line ) , is a line in the Barcelona Metro network operated by TMB , and part of the ATM fare-integrated transport network .