Narrative:

While taxiing from our gate to hold spot D we were told to contact ground control, which we did. The ground controller told us to follow an MD80 from right to left at taxiway east. We saw 2 MD80's and asked for clarification. They said to us to turn right and proceed behind the MD80 at taxiway east. That aircraft was holding short of runway 12R at taxiway east. Runways 12R&left were active runways. Ground control told the MD80 to cross runway 12R at taxiway east, and told us to taxi to taxiway a and right on taxiway C, hold short of runway 12R at taxiway C. The first officer acknowledged this. I did not hear, turn left on taxiway a, but thought I heard turn left on taxiway C, which I found on the other side of runway 12R. I crossed runway 12R behind the MD80. Ground control said to us that he wanted us on taxiway C which was off my left. Then another controller told us to call the tower when we get to our destination. As I taxied across runway 12R, I saw out my left window the landing lights of an approaching aircraft, so I expedited across. After reaching cruise altitude I talked this over with the first officer. Upon further examination of the taxi diagram, I then realized what the controller wanted us to do. Upon reaching the destination airport I called stl tower on the phone and spoke with the supervisor. I apologized and said I realized what my mistake was. He was nice about it and said there was no violation of separation, but it was close. He suggested that there must have been some confusion in our cockpit because the first officer read the clearance back correctly. I agreed and remembered that when in doubt, don't move the aircraft until both pilots agree on the instructions. This was a very good lesson for me. The controller agreed and said that there would be no violation because of no violation of separation, my prompt phone call and my attitude.

Related reports:

Google
 

Original NASA ASRS Text

Title: DC9 PIC MISUNDERSTOOD TAXI CLRNC AND CROSSED RWY 12R WITHOUT CLRNC. FO HAD READ BACK CORRECT CLRNC.

Narrative: WHILE TAXIING FROM OUR GATE TO HOLD SPOT D WE WERE TOLD TO CONTACT GND CTL, WHICH WE DID. THE GND CTLR TOLD US TO FOLLOW AN MD80 FROM R TO L AT TXWY E. WE SAW 2 MD80'S AND ASKED FOR CLARIFICATION. THEY SAID TO US TO TURN R AND PROCEED BEHIND THE MD80 AT TXWY E. THAT ACFT WAS HOLDING SHORT OF RWY 12R AT TXWY E. RWYS 12R&L WERE ACTIVE RWYS. GND CTL TOLD THE MD80 TO CROSS RWY 12R AT TXWY E, AND TOLD US TO TAXI TO TXWY A AND R ON TXWY C, HOLD SHORT OF RWY 12R AT TXWY C. THE FO ACKNOWLEDGED THIS. I DID NOT HEAR, TURN L ON TXWY A, BUT THOUGHT I HEARD TURN L ON TXWY C, WHICH I FOUND ON THE OTHER SIDE OF RWY 12R. I CROSSED RWY 12R BEHIND THE MD80. GND CTL SAID TO US THAT HE WANTED US ON TXWY C WHICH WAS OFF MY L. THEN ANOTHER CTLR TOLD US TO CALL THE TWR WHEN WE GET TO OUR DEST. AS I TAXIED ACROSS RWY 12R, I SAW OUT MY L WINDOW THE LNDG LIGHTS OF AN APCHING ACFT, SO I EXPEDITED ACROSS. AFTER REACHING CRUISE ALT I TALKED THIS OVER WITH THE FO. UPON FURTHER EXAMINATION OF THE TAXI DIAGRAM, I THEN REALIZED WHAT THE CTLR WANTED US TO DO. UPON REACHING THE DEST ARPT I CALLED STL TWR ON THE PHONE AND SPOKE WITH THE SUPVR. I APOLOGIZED AND SAID I REALIZED WHAT MY MISTAKE WAS. HE WAS NICE ABOUT IT AND SAID THERE WAS NO VIOLATION OF SEPARATION, BUT IT WAS CLOSE. HE SUGGESTED THAT THERE MUST HAVE BEEN SOME CONFUSION IN OUR COCKPIT BECAUSE THE FO READ THE CLRNC BACK CORRECTLY. I AGREED AND REMEMBERED THAT WHEN IN DOUBT, DON'T MOVE THE ACFT UNTIL BOTH PLTS AGREE ON THE INSTRUCTIONS. THIS WAS A VERY GOOD LESSON FOR ME. THE CTLR AGREED AND SAID THAT THERE WOULD BE NO VIOLATION BECAUSE OF NO VIOLATION OF SEPARATION, MY PROMPT PHONE CALL AND MY ATTITUDE.

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.