Narrative:

During taxi from overnight parking location at chicago midway airport to a gate across the airfield. As first officer, I obtained taxi clearance from ground control. We were cleared to taxi, 'hold short of runway 31L.' after clearing the parking spot onto the taxiway, the captain asked, 'hold short of which runway?' I responded with runway '31C.' it is common to use runways 31L and 31R as txwys when runway 31C is in use and I responded with what I thought was the correct hold short runway. Without confirming hold short runway, we taxied across runway 31L and held short of runway 31C. Ground control called 'stop' when they observed our aircraft already across runway 31L. We held short of runway 31C and waited further clearance to taxi. The problem resulted from the failure to reconfirm taxi instructions from ground control even though there was sufficient time. I allowed a confusing situation to go uncorrected by using what I assumed to be the hold short instructions instead of reconfirming with ground control.

Related reports:

Google
 

Original NASA ASRS Text

Title: FLC OF AN MLG FAILED TO STOP SHORT OF RWY DURING THE REPOSITIONING OF AN OVERNIGHT PARKING TO THE GATE.

Narrative: DURING TAXI FROM OVERNIGHT PARKING LOCATION AT CHICAGO MIDWAY ARPT TO A GATE ACROSS THE AIRFIELD. AS FO, I OBTAINED TAXI CLRNC FROM GND CTL. WE WERE CLRED TO TAXI, 'HOLD SHORT OF RWY 31L.' AFTER CLRING THE PARKING SPOT ONTO THE TXWY, THE CAPT ASKED, 'HOLD SHORT OF WHICH RWY?' I RESPONDED WITH RWY '31C.' IT IS COMMON TO USE RWYS 31L AND 31R AS TXWYS WHEN RWY 31C IS IN USE AND I RESPONDED WITH WHAT I THOUGHT WAS THE CORRECT HOLD SHORT RWY. WITHOUT CONFIRMING HOLD SHORT RWY, WE TAXIED ACROSS RWY 31L AND HELD SHORT OF RWY 31C. GND CTL CALLED 'STOP' WHEN THEY OBSERVED OUR ACFT ALREADY ACROSS RWY 31L. WE HELD SHORT OF RWY 31C AND WAITED FURTHER CLRNC TO TAXI. THE PROB RESULTED FROM THE FAILURE TO RECONFIRM TAXI INSTRUCTIONS FROM GND CTL EVEN THOUGH THERE WAS SUFFICIENT TIME. I ALLOWED A CONFUSING SIT TO GO UNCORRECTED BY USING WHAT I ASSUMED TO BE THE HOLD SHORT INSTRUCTIONS INSTEAD OF RECONFIRMING WITH GND CTL.

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.