Narrative:

The flight was bos to las. I was the first officer. We departed bos on time and the flight to las was uneventful. The WX was VMC throughout the approach; but it was well past dark. The night visual approach was conducted to runway 25L and landing went normally. We turned off the runway at taxiway A7 and were instructed to taxi on taxiway a to taxiway A5 and hold short of runway 25R; which we did. I accomplished the after landing checklist and then we were cleared to cross runway 25R and instructed to call ground. Ground instructed us to taxi to taxiway C5 and contact ramp control. The captain made a right turn onto taxiway B off of taxiway A5. At this time; the captain mistook the infield area between taxiway B5 and taxiway B4 for the taxiway C/ramp area and made a left turn at about a 45 degree angle and taxied across the unprepared surface. By the time I recognized where we were headed; we were already off the taxiway. Another aircraft reported that a cloud of dust had blown up behind the aircraft. I admit that even though I was looking at the unprepared area in the taxi light; it is very hard to distinguish the concrete from the dirt. There was a slight rocking of the aircraft when we went across the area; but it was not significant. We crossed the area quickly and were on taxiway C. We taxied to the gate and wrote up in the log book the taxiing excursion. Inspection showed no damage to the aircraft but light coating of dust on the tire edges confirmed we had been in the dirt. First of all; it is very difficult to distinguish the taxiway edge visually. The color of the unprepared surface is close to that of concrete. Second; there are almost no blue taxiway edge markers. Third; the lines are almost washed out. This may be due to dust on the taxiway or maybe they need to be repainted. That whole area of the airport is almost a black hole. Still; we should have stayed on the yellow line.supplemental information from acn 702149: ground control instructed another aircraft to 'hold short for air carrier X crossing right to left ahead.' I scanned the txwys to the left to ensure no conflict would develop with that aircraft. I then initiated the right turn onto taxiway C; moving right of the taxiway centerline to make a smoother angular transition. The intersection appeared to be very large and it was a very dark area of the taxiway; with no taxiway edge lights. As I continued to scan for other traffic in all directions; I suddenly realized that we were off the taxiway and in the unprepared dirt surface. The surface was very similar in color and contrast to the taxiway; and; fortunately; very firm and fairly level with the taxiway. We had just caught the very corner of the dirt surface; with both main gear having left the taxiway. As quickly as I realized that we were on the unprepared surface; we were just as quickly back on the taxiway.callback conversation with rptrs revealed the following information: rptrs stated that the txwys are marked with blue reflector poles vice blue taxiway lights and that the lighting was very poor. The blue poles are difficult to distinguish and the aircraft's taxi light was the only source of lighting at times. The rptrs did mention that the use of the landing lights would have assisted; however; normal procedures are to turn the landing lights off after exiting the runway to prevent blinding other aircraft. Additionally; the rptrs indicated that the yellow taxiway lines were faded and they assumed that the area they were taxiing in was a large; open taxiway as indicated on the charts.

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Original NASA ASRS Text

Title: A B737-800 FLT CREW CITES INADEQUATE TXWY LIGHTING/MARKINGS AT LAS AS CONTRIBUTING TO A TXWY EXCURSION.

Narrative: THE FLT WAS BOS TO LAS. I WAS THE FO. WE DEPARTED BOS ON TIME AND THE FLT TO LAS WAS UNEVENTFUL. THE WX WAS VMC THROUGHOUT THE APCH; BUT IT WAS WELL PAST DARK. THE NIGHT VISUAL APCH WAS CONDUCTED TO RWY 25L AND LNDG WENT NORMALLY. WE TURNED OFF THE RWY AT TXWY A7 AND WERE INSTRUCTED TO TAXI ON TXWY A TO TXWY A5 AND HOLD SHORT OF RWY 25R; WHICH WE DID. I ACCOMPLISHED THE AFTER LNDG CHKLIST AND THEN WE WERE CLRED TO CROSS RWY 25R AND INSTRUCTED TO CALL GND. GND INSTRUCTED US TO TAXI TO TXWY C5 AND CONTACT RAMP CTL. THE CAPT MADE A R TURN ONTO TXWY B OFF OF TXWY A5. AT THIS TIME; THE CAPT MISTOOK THE INFIELD AREA BETWEEN TXWY B5 AND TXWY B4 FOR THE TXWY C/RAMP AREA AND MADE A L TURN AT ABOUT A 45 DEG ANGLE AND TAXIED ACROSS THE UNPREPARED SURFACE. BY THE TIME I RECOGNIZED WHERE WE WERE HEADED; WE WERE ALREADY OFF THE TXWY. ANOTHER ACFT RPTED THAT A CLOUD OF DUST HAD BLOWN UP BEHIND THE ACFT. I ADMIT THAT EVEN THOUGH I WAS LOOKING AT THE UNPREPARED AREA IN THE TAXI LIGHT; IT IS VERY HARD TO DISTINGUISH THE CONCRETE FROM THE DIRT. THERE WAS A SLIGHT ROCKING OF THE ACFT WHEN WE WENT ACROSS THE AREA; BUT IT WAS NOT SIGNIFICANT. WE CROSSED THE AREA QUICKLY AND WERE ON TXWY C. WE TAXIED TO THE GATE AND WROTE UP IN THE LOG BOOK THE TAXIING EXCURSION. INSPECTION SHOWED NO DAMAGE TO THE ACFT BUT LIGHT COATING OF DUST ON THE TIRE EDGES CONFIRMED WE HAD BEEN IN THE DIRT. FIRST OF ALL; IT IS VERY DIFFICULT TO DISTINGUISH THE TXWY EDGE VISUALLY. THE COLOR OF THE UNPREPARED SURFACE IS CLOSE TO THAT OF CONCRETE. SECOND; THERE ARE ALMOST NO BLUE TXWY EDGE MARKERS. THIRD; THE LINES ARE ALMOST WASHED OUT. THIS MAY BE DUE TO DUST ON THE TXWY OR MAYBE THEY NEED TO BE REPAINTED. THAT WHOLE AREA OF THE ARPT IS ALMOST A BLACK HOLE. STILL; WE SHOULD HAVE STAYED ON THE YELLOW LINE.SUPPLEMENTAL INFO FROM ACN 702149: GND CTL INSTRUCTED ANOTHER ACFT TO 'HOLD SHORT FOR ACR X CROSSING R TO L AHEAD.' I SCANNED THE TXWYS TO THE L TO ENSURE NO CONFLICT WOULD DEVELOP WITH THAT ACFT. I THEN INITIATED THE R TURN ONTO TXWY C; MOVING R OF THE TXWY CTRLINE TO MAKE A SMOOTHER ANGULAR TRANSITION. THE INTXN APPEARED TO BE VERY LARGE AND IT WAS A VERY DARK AREA OF THE TXWY; WITH NO TXWY EDGE LIGHTS. AS I CONTINUED TO SCAN FOR OTHER TFC IN ALL DIRECTIONS; I SUDDENLY REALIZED THAT WE WERE OFF THE TXWY AND IN THE UNPREPARED DIRT SURFACE. THE SURFACE WAS VERY SIMILAR IN COLOR AND CONTRAST TO THE TXWY; AND; FORTUNATELY; VERY FIRM AND FAIRLY LEVEL WITH THE TXWY. WE HAD JUST CAUGHT THE VERY CORNER OF THE DIRT SURFACE; WITH BOTH MAIN GEAR HAVING LEFT THE TXWY. AS QUICKLY AS I REALIZED THAT WE WERE ON THE UNPREPARED SURFACE; WE WERE JUST AS QUICKLY BACK ON THE TXWY.CALLBACK CONVERSATION WITH RPTRS REVEALED THE FOLLOWING INFO: RPTRS STATED THAT THE TXWYS ARE MARKED WITH BLUE REFLECTOR POLES VICE BLUE TXWY LIGHTS AND THAT THE LIGHTING WAS VERY POOR. THE BLUE POLES ARE DIFFICULT TO DISTINGUISH AND THE ACFT'S TAXI LIGHT WAS THE ONLY SOURCE OF LIGHTING AT TIMES. THE RPTRS DID MENTION THAT THE USE OF THE LNDG LIGHTS WOULD HAVE ASSISTED; HOWEVER; NORMAL PROCS ARE TO TURN THE LNDG LIGHTS OFF AFTER EXITING THE RWY TO PREVENT BLINDING OTHER ACFT. ADDITIONALLY; THE RPTRS INDICATED THAT THE YELLOW TXWY LINES WERE FADED AND THEY ASSUMED THAT THE AREA THEY WERE TAXIING IN WAS A LARGE; OPEN TXWY AS INDICATED ON THE CHARTS.

Data retrieved from NASA's ASRS site as of January 2009 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.