B737 flight crew misinterped clearance and taxied across runway. Aircraft on final issued go around.

Attributes
ACN	471668
Time
Date	200005
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : mdw.airport
State Reference	IL
Altitude	agl single value : 0
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : mdw.tower tower : egll.tower
Operator	common carrier : air carrier
Make Model Name	B737-200
Operating Under FAR Part	Part 121
Flight Phase	ground : taxi
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tower : mdw.tower
Make Model Name	Small Aircraft
Flight Phase	descent : approach
Route In Use	approach : straight in
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 300 flight time total : 4500 flight time type : 450
ASRS Report	471668
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : commercial
Experience	flight time last 90 days : 100 flight time total : 10500 flight time type : 3500
ASRS Report	471789
Events
Anomaly	conflict : ground less severe incursion : runway non adherence : clearance
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance controller : separated traffic flight crew : executed go around
Consequence	faa : reviewed incident with flight crew
Miss Distance	horizontal : 6000
Supplementary
Problem Areas	Flight Crew Human Performance Airport
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Taxiing from gate Y at mdw to runway 31C. Captain only heard 'taxi to runway 31C.' however, as we approached runway 31R, captain asked me if we were cleared all the way to runway 31C. I understood runway 31R, so I said yes. In the confusion I realized he asked me runway 31C and I said that we have to hold short of runway 31R. Captain stopped the airplane about 15 ft over the hold line and advised ATC. They asked for confirmation that we were over the line and directed a small aircraft to go around about 1 mi on final. From this I have learned to never take for granted the communication with the crew. When we had the clearance to taxi and hold short of runway 31R, I read it back and told the captain. He never confirmed or replied my input and I took for granted he'd listen. Also, I learned to think before speaking, because when he asked me 'are we cleared to runway 31C?' I understood runway 31R and said yes, and we were too close to the hold line and ended up over it.

Original NASA ASRS Text

Title: B737 FLC MISINTERPED CLRNC AND TAXIED ACROSS RWY. ACFT ON FINAL ISSUED GAR.

Narrative: TAXIING FROM GATE Y AT MDW TO RWY 31C. CAPT ONLY HEARD 'TAXI TO RWY 31C.' HOWEVER, AS WE APCHED RWY 31R, CAPT ASKED ME IF WE WERE CLRED ALL THE WAY TO RWY 31C. I UNDERSTOOD RWY 31R, SO I SAID YES. IN THE CONFUSION I REALIZED HE ASKED ME RWY 31C AND I SAID THAT WE HAVE TO HOLD SHORT OF RWY 31R. CAPT STOPPED THE AIRPLANE ABOUT 15 FT OVER THE HOLD LINE AND ADVISED ATC. THEY ASKED FOR CONFIRMATION THAT WE WERE OVER THE LINE AND DIRECTED A SMALL ACFT TO GO AROUND ABOUT 1 MI ON FINAL. FROM THIS I HAVE LEARNED TO NEVER TAKE FOR GRANTED THE COM WITH THE CREW. WHEN WE HAD THE CLRNC TO TAXI AND HOLD SHORT OF RWY 31R, I READ IT BACK AND TOLD THE CAPT. HE NEVER CONFIRMED OR REPLIED MY INPUT AND I TOOK FOR GRANTED HE'D LISTEN. ALSO, I LEARNED TO THINK BEFORE SPEAKING, BECAUSE WHEN HE ASKED ME 'ARE WE CLRED TO RWY 31C?' I UNDERSTOOD RWY 31R AND SAID YES, AND WE WERE TOO CLOSE TO THE HOLD LINE AND ENDED UP OVER IT.

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.