Narrative:

Ground control told us (air carrier large transport) to expedite taxi and cross runway 4L at the end, traffic on final. Because of construction, we had to taxi and cross runway 4L at the very end of the displaced threshold, where there's a lot of paved surface that is not marked well, nor is there good signage. I saw the air carrier Z light transport twin engine on short final as I turned the corner. I did not like the separation, so I stopped, expecting to hold short of runway 4L. In fact, I stopped in the middle of the displaced threshold. Even though I realized my mistake and continued taxiing, the engines did not spool up quickly, and tower told the commuter to go around. He said he could fly over us and continue since we were (by then) moving again. I'm not sure if he went around. Boston is not an easy place to taxi out for runway 9 because one must cross runway 4L/22R at sierra. By having us go beyond sierra and cross at the end because of construction, the extended centerline of runway 4L/22R, meaning the displaced threshold area, is very hard to define. I was not happy with the expedited taxi clearance, yet I ended up exacerbating events by stopping smack in the middle. Also, I am a check airman, and this was the very first leg of a boston first officer's IOE. Next time, I will not accept an expedited clearance. I'll just taxi normally and hold short. With a student, I need a slower pace.

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Original NASA ASRS Text

Title: AN LGT STOPPED IN THE MIDDLE OF THE DISPLACED THRESHOLD OF THE LNDG RWY CAUSING AN LTT TO TAKE EVASIVE ACTION.

Narrative: GND CTL TOLD US (ACR LGT) TO EXPEDITE TAXI AND CROSS RWY 4L AT THE END, TFC ON FINAL. BECAUSE OF CONSTRUCTION, WE HAD TO TAXI AND CROSS RWY 4L AT THE VERY END OF THE DISPLACED THRESHOLD, WHERE THERE'S A LOT OF PAVED SURFACE THAT IS NOT MARKED WELL, NOR IS THERE GOOD SIGNAGE. I SAW THE ACR Z LTT TWIN ENG ON SHORT FINAL AS I TURNED THE CORNER. I DID NOT LIKE THE SEPARATION, SO I STOPPED, EXPECTING TO HOLD SHORT OF RWY 4L. IN FACT, I STOPPED IN THE MIDDLE OF THE DISPLACED THRESHOLD. EVEN THOUGH I REALIZED MY MISTAKE AND CONTINUED TAXIING, THE ENGS DID NOT SPOOL UP QUICKLY, AND TWR TOLD THE COMMUTER TO GAR. HE SAID HE COULD FLY OVER US AND CONTINUE SINCE WE WERE (BY THEN) MOVING AGAIN. I'M NOT SURE IF HE WENT AROUND. BOSTON IS NOT AN EASY PLACE TO TAXI OUT FOR RWY 9 BECAUSE ONE MUST CROSS RWY 4L/22R AT SIERRA. BY HAVING US GO BEYOND SIERRA AND CROSS AT THE END BECAUSE OF CONSTRUCTION, THE EXTENDED CTRLINE OF RWY 4L/22R, MEANING THE DISPLACED THRESHOLD AREA, IS VERY HARD TO DEFINE. I WAS NOT HAPPY WITH THE EXPEDITED TAXI CLRNC, YET I ENDED UP EXACERBATING EVENTS BY STOPPING SMACK IN THE MIDDLE. ALSO, I AM A CHK AIRMAN, AND THIS WAS THE VERY FIRST LEG OF A BOSTON FO'S IOE. NEXT TIME, I WILL NOT ACCEPT AN EXPEDITED CLRNC. I'LL JUST TAXI NORMALLY AND HOLD SHORT. WITH A STUDENT, I NEED A SLOWER PACE.

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.