Narrative:

We pushed back from the gate at sfo and started engines. We called ground and received a taxi clearance 'taxi to runway 10L via txwys a; east; B; Z; and south.' we reviewed our diagrams and started our taxi. We were on taxiway a so we followed it northbound until we intercepted taxiway east; made the dogleg on taxiway east to intercept taxiway B; followed taxiway B westbound and continued westbound when it turned into taxiway Z. My understanding of the clearance was that we were cleared to taxi on taxiway Z until reaching taxiway south; then to follow taxiway south to the threshold of runway 10L; and hold short. Looking at the chart; the only place I saw taxiway south was to the northeast of runway 10L; so I planned to follow taxiway Z around the end of both runways 10R and 10L; then intercept taxiway south. Oops; it turns out there is a small segment of taxiway south that runs from taxiway Z to the threshold of runway 10R; and continues to the threshold of runway 10L. We passed the first intersection of taxiway south; the ground controller spotted us; and he had us turn on to taxiway S2 to intercept taxiway south; and hold short of runway 10L. I think that taxiway south should be relabeled on either the left side of runway 10L; or the right side of runway 10L (which leads to runway 10R); or there is a potential that another aircraft could do the same thing; and possibly have a conflict. It doesn't; to me; make sense to have the txwys marked in such a way that a clearance can be interpreted in two different ways; so that the pilot and controller are not clear on what is expected; or what will happen.callback conversation with reporter revealed the following information: reporter indicated that the flight crew had not operated from that area or runway previously. Due to the wind and WX conditions the airport was on south operations and the reporter never encountered this runway direction. WX was rainy and the txwys were wet; causing some confusion with the lines and directions. The reporter indicated that his and his first officer's lack of familiarity with the airport operations from that runway was the primary cause of the confusion. However; his concern was that the multiple ways to arrive at the runway via the taxiway south is confusing and he said that changing the taxiway designation may help with the confusion.

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Original NASA ASRS Text

Title: B767 FLT CREW RPTS CONFUSION WITH TAXI CLRNC AT SFO INVOLVING TWO TXWYS LABELED 'S' LOCATED ON OPPOSITE SIDES OF RWY 10L.

Narrative: WE PUSHED BACK FROM THE GATE AT SFO AND STARTED ENGS. WE CALLED GND AND RECEIVED A TAXI CLRNC 'TAXI TO RWY 10L VIA TXWYS A; E; B; Z; AND S.' WE REVIEWED OUR DIAGRAMS AND STARTED OUR TAXI. WE WERE ON TXWY A SO WE FOLLOWED IT NORTHBOUND UNTIL WE INTERCEPTED TXWY E; MADE THE DOGLEG ON TXWY E TO INTERCEPT TXWY B; FOLLOWED TXWY B WESTBOUND AND CONTINUED WESTBOUND WHEN IT TURNED INTO TXWY Z. MY UNDERSTANDING OF THE CLRNC WAS THAT WE WERE CLRED TO TAXI ON TXWY Z UNTIL REACHING TXWY S; THEN TO FOLLOW TXWY S TO THE THRESHOLD OF RWY 10L; AND HOLD SHORT. LOOKING AT THE CHART; THE ONLY PLACE I SAW TXWY S WAS TO THE NORTHEAST OF RWY 10L; SO I PLANNED TO FOLLOW TXWY Z AROUND THE END OF BOTH RWYS 10R AND 10L; THEN INTERCEPT TXWY S. OOPS; IT TURNS OUT THERE IS A SMALL SEGMENT OF TXWY S THAT RUNS FROM TXWY Z TO THE THRESHOLD OF RWY 10R; AND CONTINUES TO THE THRESHOLD OF RWY 10L. WE PASSED THE FIRST INTXN OF TXWY S; THE GND CTLR SPOTTED US; AND HE HAD US TURN ON TO TXWY S2 TO INTERCEPT TXWY S; AND HOLD SHORT OF RWY 10L. I THINK THAT TXWY S SHOULD BE RELABELED ON EITHER THE LEFT SIDE OF RWY 10L; OR THE RIGHT SIDE OF RWY 10L (WHICH LEADS TO RWY 10R); OR THERE IS A POTENTIAL THAT ANOTHER ACFT COULD DO THE SAME THING; AND POSSIBLY HAVE A CONFLICT. IT DOESN'T; TO ME; MAKE SENSE TO HAVE THE TXWYS MARKED IN SUCH A WAY THAT A CLRNC CAN BE INTERPRETED IN TWO DIFFERENT WAYS; SO THAT THE PLT AND CTLR ARE NOT CLR ON WHAT IS EXPECTED; OR WHAT WILL HAPPEN.CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR INDICATED THAT THE FLT CREW HAD NOT OPERATED FROM THAT AREA OR RWY PREVIOUSLY. DUE TO THE WIND AND WX CONDITIONS THE ARPT WAS ON SOUTH OPERATIONS AND THE RPTR NEVER ENCOUNTERED THIS RWY DIRECTION. WX WAS RAINY AND THE TXWYS WERE WET; CAUSING SOME CONFUSION WITH THE LINES AND DIRECTIONS. THE RPTR INDICATED THAT HIS AND HIS FO'S LACK OF FAMILIARITY WITH THE ARPT OPERATIONS FROM THAT RWY WAS THE PRIMARY CAUSE OF THE CONFUSION. HOWEVER; HIS CONCERN WAS THAT THE MULTIPLE WAYS TO ARRIVE AT THE RWY VIA THE TXWY S IS CONFUSING AND HE SAID THAT CHANGING THE TXWY DESIGNATION MAY HELP WITH THE CONFUSION.

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.