Narrative:

This was the last leg of a very long 4 day trip. Mdw to ewr. At the time of occurrence we had blocked 27 hours in 4 days and on arrival in ewr 29 hours 19 mins. The previous duty day was 13 hours 45 mins and on day of occurrence over 13 hours again. We were tired, very tired and this was certainly a major factor. We received taxi clearance to taxi to runway 31C via taxiway P. Both the captain and myself were confused by the 'new' signage at midway. There seemed to be a lot of signage close together and it was difficult to figure which taxiway went with which sign. I checked the taxi chart and told the captain we should be heading 180 degrees once on taxiway P. On taxiway P and taxiing south we crossed runway 31R and before we knew it, had crossed the active runway 31C. We missed taxiway G that would have taken us to runway 31C. As copilot I would normally be doing taxi checks but was not. I was outside with the captain and we both got confused on this taxi out. After crossing runway 31C (the active) ground control called out our error and turned us around. Thankfully there was no conflict with another aircraft. I believe this taxi error occurred for the following reasons: pilot not familiar with midway. When there was confusion about taxi instructions the aircraft should have been stopped until resolved. Fatigue. Ground control monitoring aircraft movement. We were the only aircraft moving on the field at the time. Midway airport design. Runways close together and taxi signs difficult to understand.

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Original NASA ASRS Text

Title: FLC OF A B737 INADVERTENTLY TAXIED ACROSS THE ACTIVE RWY DURING TAXI OUT FOR TKOF. THERE WAS NO CONFLICT AND THE TWR CTLR TURNED THEM AROUND AND HEADED DOWN THE CORRECT TXWY.

Narrative: THIS WAS THE LAST LEG OF A VERY LONG 4 DAY TRIP. MDW TO EWR. AT THE TIME OF OCCURRENCE WE HAD BLOCKED 27 HRS IN 4 DAYS AND ON ARR IN EWR 29 HRS 19 MINS. THE PREVIOUS DUTY DAY WAS 13 HRS 45 MINS AND ON DAY OF OCCURRENCE OVER 13 HRS AGAIN. WE WERE TIRED, VERY TIRED AND THIS WAS CERTAINLY A MAJOR FACTOR. WE RECEIVED TAXI CLRNC TO TAXI TO RWY 31C VIA TXWY P. BOTH THE CAPT AND MYSELF WERE CONFUSED BY THE 'NEW' SIGNAGE AT MIDWAY. THERE SEEMED TO BE A LOT OF SIGNAGE CLOSE TOGETHER AND IT WAS DIFFICULT TO FIGURE WHICH TXWY WENT WITH WHICH SIGN. I CHKED THE TAXI CHART AND TOLD THE CAPT WE SHOULD BE HDG 180 DEGS ONCE ON TXWY P. ON TXWY P AND TAXIING S WE CROSSED RWY 31R AND BEFORE WE KNEW IT, HAD CROSSED THE ACTIVE RWY 31C. WE MISSED TXWY G THAT WOULD HAVE TAKEN US TO RWY 31C. AS COPLT I WOULD NORMALLY BE DOING TAXI CHKS BUT WAS NOT. I WAS OUTSIDE WITH THE CAPT AND WE BOTH GOT CONFUSED ON THIS TAXI OUT. AFTER XING RWY 31C (THE ACTIVE) GND CTL CALLED OUT OUR ERROR AND TURNED US AROUND. THANKFULLY THERE WAS NO CONFLICT WITH ANOTHER ACFT. I BELIEVE THIS TAXI ERROR OCCURRED FOR THE FOLLOWING REASONS: PLT NOT FAMILIAR WITH MIDWAY. WHEN THERE WAS CONFUSION ABOUT TAXI INSTRUCTIONS THE ACFT SHOULD HAVE BEEN STOPPED UNTIL RESOLVED. FATIGUE. GND CTL MONITORING ACFT MOVEMENT. WE WERE THE ONLY ACFT MOVING ON THE FIELD AT THE TIME. MIDWAY ARPT DESIGN. RWYS CLOSE TOGETHER AND TAXI SIGNS DIFFICULT TO UNDERSTAND.

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.