Narrative:

The captain misconstrued lights from 2 parallel txwys as delineating an intersecting taxiway and taxied off the hard surface onto the median between the txwys. Conditions were: night, snow and blowing snow (20 mph winds), 6 inches of snow on unplowed txwys and markings obscured, 1/4 mi visibility. Following deicing en route to the runway the taxiway excursion occurred. More emphasis should be placed on closing facilities when they can't be adequately cleared of snow. If the lights facing away from the taxiway were made to appear differently from the lights you see while on the taxiway, better situational awareness would be possible.

Related reports:

Google
 

Original NASA ASRS Text

Title: B727 ACFT TAXIING FROM DEICING PAD, CAPT BECAME CONFUSED BY SNOW COVERED TXWYS AND TXWY LIGHTING AND TXWY EXCURSION OCCURRED.

Narrative: THE CAPT MISCONSTRUED LIGHTS FROM 2 PARALLEL TXWYS AS DELINEATING AN INTERSECTING TXWY AND TAXIED OFF THE HARD SURFACE ONTO THE MEDIAN BTWN THE TXWYS. CONDITIONS WERE: NIGHT, SNOW AND BLOWING SNOW (20 MPH WINDS), 6 INCHES OF SNOW ON UNPLOWED TXWYS AND MARKINGS OBSCURED, 1/4 MI VISIBILITY. FOLLOWING DEICING ENRTE TO THE RWY THE TXWY EXCURSION OCCURRED. MORE EMPHASIS SHOULD BE PLACED ON CLOSING FACILITIES WHEN THEY CAN'T BE ADEQUATELY CLRED OF SNOW. IF THE LIGHTS FACING AWAY FROM THE TXWY WERE MADE TO APPEAR DIFFERENTLY FROM THE LIGHTS YOU SEE WHILE ON THE TXWY, BETTER SITUATIONAL AWARENESS WOULD BE POSSIBLE.

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.