B767 CAPT BECOMES DISORIENTED WHILE TAXIING OUT AND OVERSHOT RWY HOLD SHORT LINE. HOWEVER; THE TWR CTLR PERMITTED A LNDG ACFT TO ROLL PAST AND ANOTHER TO DEPART BEFORE MOVING HIM ACROSS THE RWY.

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I WAS THE COPLT FOR ACFT X FLT XXXX ON FEB/TUE/02 FROM STL TO LGW. WE PUSHED BACK FROM THE GATE IN STL AND WERE FACING TAIL W ON THE INNER AIRLINE RAMP. AFTER BEING CLRED BY GND TO TAXI TO RWY 12L VIA TXWY A HOLD SHORT OF THE RWY 12R AT TXWY E; WE BEGAN OUR TAXI. THE CAPT MADE A L TURN TO JOIN TXWY A AND I INFORMED HIM THAT I WOULD BE HEADS DOWN AND BEGAN THE PROCESS OF UPDATING THE FMC WITH THE NEW CLOSEOUT WTS. I LOOKED UP TO SEE THE RED RWY SIGN OUT OF MY PERIPHERAL VISION AND THE YELLOW RWY HOLD SHORT LINES COMING UP QUICKLY. JUST AS I WAS ABOUT TO TELL HIM TO STOP; THE GND CTLR TOLD US TO STOP. THE NOSE OF THE PLANE WAS PROBABLY 5 FT OVER THE YELLOW HOLD LINE AT TXWY H. AN MD80 ON ROLLOUT TAXIED BY US AND THE TWR DEPARTED ANOTHER PLANE BEFORE GIVING US INSTRUCTIONS TO CROSS RWY 12L AT TXWY H. THE CAPT LATER STATED THAT HE KNEW THAT HE HAD TO TURN AROUND A GRASS ISLAND TO GET TO TXWY A. BUT WE WERE PUSHED BACK TO THE N SIDE OF THE AIRLINE RAMP AND THE CAPT MISSED THE ISLAND THAT HE WAS LOOKING FOR AND INSTEAD TURNED AROUND THE ISLAND THAT SEPARATED TXWY A AND RWY 12R. CONTRIBUTING FACTORS: 1) I AM A NEW COPLT ON THE AIRPLANE AND WAS RECEIVING IOE THAT NIGHT. 2) WE GOT TO THE PLANE 1/2 HR BEFORE DEP DUE TO THE FACT THAT WE ARE USING PAPERWORK AND IT TOOK US LONGER TO LOCATE THE INFO THAT WE NEEDED TO WORK THE FLT. 3) THE CHANGE IN CALL SIGNS FROM XXXX TO YYYY REQUIRES EXTRA THOUGHT INSTEAD OF JUST BEING ABLE TO RESPOND NATURALLY. 4) USING 4 DIGIT CALL SIGNS INSTEAD OF 2 OR 3 ALSO CAUSES A BREAK IN HABIT PATTERNS. 5) BOTH ME AND THE THIRD PLT IN THE COCKPIT SHOULD HAVE NOT DONE ANY EXTRA PAPERWORK UNTIL WE WERE SURE THAT THE CAPT WAS ON TXWY A. THE THIRD PLT AND MYSELF WERE BOTH CHKED OUT AS CAPTS ON THE B717.