Narrative:

While taxiing out of pit our ramp exit was very close to the taxiway and runway 28/10C. Ground issued a clearance to runway 28C via taxiway east with a clearance to cross runway 32. Due to a heavy workload in the cockpit and difficulty seeing the taxiway signs due to snow build-up, we misunderstood ground control's instructions as a clearance to cross runway 28C to runway 28L via taxiway east. I thought taxiway east was the parallel taxiway between runways 28C and 28L, and while I had my head down checking the airport diagram, the captain continued his taxi across runway 28C. After crossing the active runway, I saw an aircraft taxi into position and I realized our error at which point ground control questioned our actions. We were cleared to runway 28L without further incident. This was an avoidable human error and resulted from an excitable captain, dusk conditions, contaminated airport conditions, confusion as to our position and clearance and my own lack of forcefulness in being more assertive with this particular captain.

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Original NASA ASRS Text

Title: TAXI CLRNC MISUNDERSTANDING. ACFT TAXIED ACROSS ACTIVE RWY WITHOUT CLRNC.

Narrative: WHILE TAXIING OUT OF PIT OUR RAMP EXIT WAS VERY CLOSE TO THE TXWY AND RWY 28/10C. GND ISSUED A CLRNC TO RWY 28C VIA TXWY E WITH A CLRNC TO CROSS RWY 32. DUE TO A HVY WORKLOAD IN THE COCKPIT AND DIFFICULTY SEEING THE TXWY SIGNS DUE TO SNOW BUILD-UP, WE MISUNDERSTOOD GND CTL'S INSTRUCTIONS AS A CLRNC TO CROSS RWY 28C TO RWY 28L VIA TXWY E. I THOUGHT TXWY E WAS THE PARALLEL TXWY BTWN RWYS 28C AND 28L, AND WHILE I HAD MY HEAD DOWN CHKING THE ARPT DIAGRAM, THE CAPT CONTINUED HIS TAXI ACROSS RWY 28C. AFTER XING THE ACTIVE RWY, I SAW AN ACFT TAXI INTO POS AND I REALIZED OUR ERROR AT WHICH POINT GND CTL QUESTIONED OUR ACTIONS. WE WERE CLRED TO RWY 28L WITHOUT FURTHER INCIDENT. THIS WAS AN AVOIDABLE HUMAN ERROR AND RESULTED FROM AN EXCITABLE CAPT, DUSK CONDITIONS, CONTAMINATED ARPT CONDITIONS, CONFUSION AS TO OUR POS AND CLRNC AND MY OWN LACK OF FORCEFULNESS IN BEING MORE ASSERTIVE WITH THIS PARTICULAR CAPT.

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.