MLG CROSSES RWY AFTER ACCEPTING CLRNC FOR ANOTHER ACFT.

Narrative

DURING THE MORNING PUSH IN STL WE WERE GIVEN CLRNC TO TAXI TO RWY 30R; HOLD SHORT OF RWY 30L AT TXWY H. THERE WAS A 727 HOLDING TO CROSS AT TXWY N AND A COMMUTER ACFT WAITING AT TXWY J. WE WERE STILL ABOUT 20 YARDS FROM THE HOLD SHORT AREA WHEN CLRNC TO CROSS RWY 30L WAS GIVEN TO ALL 3 ACFT. WITH THE PWR STILL UP WE BEGAN TO CROSS THE RWY AND READ BACK THE CLRNC AS FOLLOWS; 'CLR TO CROSS RWY 30L; FOLLOW THE 727; FLT CEB.' THE 727 WAS FIRST; FOLLOWED BY THE COMMUTER ACFT; THEN US; ON THE OTHER SIDE. ONCE REACHING THE OTHER SIDE; WE WERE INFORMED BY STL GND CTL THAT WE HAD NOT BEEN GIVEN CLRNC TO CROSS BUT TO CONTINUE TAXI TO RWY 30R. WE TOLD THE CTLR THAT WE UNDERSTOOD WE WERE TO FOLLOW THE 727 ON TXWY N ACROSS. SINCE TXWYS H AND N CONVERGE ON THE OTHER SIDE; THIS IS SOP AT STL. THE CTLR SAID THAT 'THE 727 WAS ON TXWY N.' WE THINK SHE WAS TELLING US THAT WE WEREN'T BEHIND THE 727 SO HOW COULD WE FOLLOW IT. THERE WAS NO ONE BEHIND THE 727 AT TXWY N AND CLRNC WAS CLRLY GIVEN TO FOLLOW HIM AND SINCE THIS IS DONE ALL THE TIME AT THIS PARTICULAR XING; WE READ THE CLRNC BACK; CHKED FOR TFC; AND CROSSED THE RWY AS CLRED. CONTRIBUTING FACTORS TO THIS OCCURRENCE WERE THAT THE 727 WAS FLT CEB AND WE WERE FLT CGB. MULTIPLE CLRNCS WERE GIVEN TO CROSS THE ACTIVE RWY AT THE SAME TIME. DURING THE MORNING PUSH IN STL IT IS EXTREMELY BUSY AND EVERYONE IS TRYING TO WORK TOGETHER TO FACILITATE A SAFE BUT SOMEWHAT EXPEDITIOUS OPERATING ENVIRONMENT. WE REMEMBER OUR CLRNC WAS TO 'EXPEDITE' ACROSS THE RWY. WHEN WE HEAR THOSE TERMS WE READ BACK THE CLRNC; CLR OURSELVES AND GO. THERE WERE NO ACFT ON FINAL AND SOMETIMES TERMS SUCH AS THAT ARE USED UNNECESSARILY AND IT DETRACTS FROM A SMOOTH OP. SUPPLEMENTAL INFORMATION FROM ACN 289654: NOTHING IS UNCOMMON ABOUT XING MANY ACFT AT THE SAME TIME BUT IT DOES GET HECTIC AT TIMES. WE HAVE TO WORK TOGETHER AT THESE BUSY ARPTS TO GET THE JOB DONE. I PERSONALLY DO NOT CROSS RWYS BASED ON CLRNC ALONE. THE DECISION IS BASED ON THE OVERALL CONTEXT OF THE SIT AT THE TIME (AS WAS THIS SIT). THIS HELPS PREVENT SITS LIKE THIS WHICH WAS APPARENTLY A MIX-UP IN CALL SIGNS.