FLC OF B727 IS CLRED TO TAXI TO RWY 1R VIA TXWY A. CONSTRUCTION DOES NOT ALLOW TAXI ON A; BUT PUTS THEM ON TXWY A1. FLC CONFUSED ABOUT POS AS THE TXWY LOOPS AROUND THE END OF THE RWY. THEY ARE ACTUALLY ALIGNED WITH RWY; BUT ON AN EXTENDED TXWY WHEN THEY REALIZE POS. TWR ASKS WHAT ARE THEIR INTENTIONS. THEN CLEARS TO TAXI FORWARD TO TKOF POS.

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SFO ARPT -- PUSHBACK FROM GATE TO TAXI A. WITH GND -- CLRED TO TAXI RWY 1R VIA A. ABEAM M; OBSERVED MAJOR CONSTRUCTION AND CONTINUED ON TXWY A. LOOKING AT CONSTRUCTION AT 'Y' OF A AND A1. PROCEEDED ON A1 AND REALIZED AT RWY 1R. TURNED L AND STOPPED AT APCH END OF 1R. HAD BEEN MONITORING TWR FREQ (120.5) SINCE ABEAM M. REALIZED OUR POS AND INITIATED CONTACT WITH TWR. THEY ASKED OUR INTENTIONS. ADVISED THEM WE HAD TAXIED TOO FAR AND ASKED THEM WHAT THEY WANTED US TO DO. TWR SAID TO PROCEED STRAIGHT AHEAD AND ADMONISHED US APPROPRIATELY NEVER TO PROCEED ONTO AN ACTIVE RWY WITHOUT PROPER CLRNC. WE ACKNOWLEDGED; AND WERE THEN CLRED FOR TKOF RWY 1R. NOTE: AIRDROME DEPICTION OF SFO WILL HELP TO UNDERSTAND ABOVE COMMENTS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATES THAT THE MAIN PROB WAS A CLRNC TO TAXI VIA A TO RWY 1R. DUE TO CONSTRUCTION THERE WAS NO WAY TO TAXI WITHOUT USING THE A1 TXWY. FLT CREW DID NOT REALIZE THEY WERE ACTUALLY ALIGNED WITH THE RWY BECAUSE OF THE EXTENSION OF THE TXWY BEYOND THE BEGINNING OF THE ACTUAL RWY. SINCE THIS IS A TKOF ONLY RWY THERE WAS REALLY NO CONFLICT; BUT CONFUSION ON THE PART OF THE FLT CREW. THEY EXPECTED TO SEE THE HOLD LINES AND DID NOT BECAUSE THE TXWY LOOPS AROUND THE RWY. THE CREW WAS DISCUSSING THE HUGE CONCRETE THAT HAD BEEN DUG UP AND THAT WAS A DEFINITE DISTRACTION.