Narrative:

Parked at gate, taxi clearance was 'taxi to runway 15R via taxiway K, taxiway left.' upon making the left turn to follow taxiway K parallel to runway 4L/22R, we were told to 'stop.' we were asked if we could make the right turn onto taxiway west to now taxi to runway 9. We acknowledged we could. We were in fact at taxiway west on taxiway K. We were cleared to taxi to runway 9 via taxiway west and taxiway south, to hold short of runway 4L. I did not hear the 'hold short of runway 4L' (we were in fact holding short of runway 4L on taxiway west when we received the clearance) and I continued to taxi taxiway west and taxiway south to runway 9. Holding short of runway 9 on taxiway south we were told again 'stop.' I replied we are stopped and holding short of runway 9 on taxiway south. The controller then advised me that he had told us to hold short of runway 4L. I apologized and he indicated it was not a problem. Being that we were already on taxiway west short of runway 4L at the time the controller changed our clearance, I feel better understanding would have occurred had we been told to hold our present position and then been given the taxi clearance to runway 9 when we were clear to taxi across runway 4L. Supplemental information from acn 455720: I believe that there were several contributing factors. First, the second taxi instructions given were incorrect. As we turned right onto taxiway west, that is where we should have held short of runway 4L. The addition of taxiway south in the instructions caused us to think taxiway south would be where we would hold short of the runway 4L. Another contributing factor was that, by changing the takeoff runway, I as the first officer was in the process of getting new performance numbers from operations on radio #2. A third contributing factor was a new captain. The captain was on his 4TH trip as a new captain. In summary, it is ultimately our responsibility as the pilots to be sure of our taxi instructions and to comply with the instructions. Fortunately, runway 4L was not an active runway.

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Original NASA ASRS Text

Title: AN ACR FLC RPT ON A RWY INCURSION WHILE TAXIING AT BOS, MA.

Narrative: PARKED AT GATE, TAXI CLRNC WAS 'TAXI TO RWY 15R VIA TXWY K, TXWY L.' UPON MAKING THE L TURN TO FOLLOW TXWY K PARALLEL TO RWY 4L/22R, WE WERE TOLD TO 'STOP.' WE WERE ASKED IF WE COULD MAKE THE R TURN ONTO TXWY W TO NOW TAXI TO RWY 9. WE ACKNOWLEDGED WE COULD. WE WERE IN FACT AT TXWY W ON TXWY K. WE WERE CLRED TO TAXI TO RWY 9 VIA TXWY W AND TXWY S, TO HOLD SHORT OF RWY 4L. I DID NOT HEAR THE 'HOLD SHORT OF RWY 4L' (WE WERE IN FACT HOLDING SHORT OF RWY 4L ON TXWY W WHEN WE RECEIVED THE CLRNC) AND I CONTINUED TO TAXI TXWY W AND TXWY S TO RWY 9. HOLDING SHORT OF RWY 9 ON TXWY S WE WERE TOLD AGAIN 'STOP.' I REPLIED WE ARE STOPPED AND HOLDING SHORT OF RWY 9 ON TXWY S. THE CTLR THEN ADVISED ME THAT HE HAD TOLD US TO HOLD SHORT OF RWY 4L. I APOLOGIZED AND HE INDICATED IT WAS NOT A PROB. BEING THAT WE WERE ALREADY ON TXWY W SHORT OF RWY 4L AT THE TIME THE CTLR CHANGED OUR CLRNC, I FEEL BETTER UNDERSTANDING WOULD HAVE OCCURRED HAD WE BEEN TOLD TO HOLD OUR PRESENT POS AND THEN BEEN GIVEN THE TAXI CLRNC TO RWY 9 WHEN WE WERE CLR TO TAXI ACROSS RWY 4L. SUPPLEMENTAL INFO FROM ACN 455720: I BELIEVE THAT THERE WERE SEVERAL CONTRIBUTING FACTORS. FIRST, THE SECOND TAXI INSTRUCTIONS GIVEN WERE INCORRECT. AS WE TURNED R ONTO TXWY W, THAT IS WHERE WE SHOULD HAVE HELD SHORT OF RWY 4L. THE ADDITION OF TXWY S IN THE INSTRUCTIONS CAUSED US TO THINK TXWY S WOULD BE WHERE WE WOULD HOLD SHORT OF THE RWY 4L. ANOTHER CONTRIBUTING FACTOR WAS THAT, BY CHANGING THE TKOF RWY, I AS THE FO WAS IN THE PROCESS OF GETTING NEW PERFORMANCE NUMBERS FROM OPS ON RADIO #2. A THIRD CONTRIBUTING FACTOR WAS A NEW CAPT. THE CAPT WAS ON HIS 4TH TRIP AS A NEW CAPT. IN SUMMARY, IT IS ULTIMATELY OUR RESPONSIBILITY AS THE PLTS TO BE SURE OF OUR TAXI INSTRUCTIONS AND TO COMPLY WITH THE INSTRUCTIONS. FORTUNATELY, RWY 4L WAS NOT AN ACTIVE RWY.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.