A PVT SMA PLT NEARLY TAKES OFF ON A TXWY AT TIW; WA; ARPT. THE CTLR STOPS HIM DURING THE LINE-UP.

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AT THE TACOMA NARROWS ARPT (TIW); I WAS CLRED BY GND CTL TO TAXI TO RWY 17 FOR DEP. I TAXIED ALONG THE BOUNDARY OF THE APRON (W SIDE) FOLLOWING A YELLOW LINE N TOWARDS RWY 17. AS I REACHED THE END OF THE APRON; THERE WAS A SOLID WHITE LINE PAINTED ON THE APRON 90 DEGS TO THE YELLOW LINE. I STOPPED AT THE WHITE LINE; CALLED THE TWR AND STATED I WAS READY FOR DEP TO THE N. TWR REPLIED; 'CLRED FOR TKOF; L-HAND DEP APPROVED.' I CHKED THE SKY FOR ACFT AND BIRDS; THERE WERE NONE. I CLOSED THE THROTTLE; TURNED THE ACFT 90 DEGS; SAW WHAT I THOUGHT WAS THE RWY AND TURNED ONTO IT. TWR CALLED 'ABORT TKOF; YOU ARE ON A TXWY.' I OPENED THE THROTTLE; AND TURNED THE ACFT AROUND. TWR AGAIN CLRED ME FOR TKOF. I TURNED OFF THE TXWY; TURNED L; SAW RWY 17; ENTERED IT AND DEPARTED. FROM THE APRON POS YOU CANNOT SEE THE TXWY OR THE RWY. I AM NOT FAMILIAR WITH THE TIW ARPT. THE TXWY RUNS PARALLEL TO THE RWY. I DID SEE THE TXWY BLUE LIGHTS WHEN I TURNED THE ACFT AROUND; BUT ON TKOF I'M FOCUSING DOWN THE RWY STRAIGHT AHEAD. I DID SEE THE DOUBLE WHITE LINES DENOTING THE THRESHOLD OF RWY 17 AFTER I TURNED OFF THE TXWY. IF THE SOLID WHITE LINE HAD NOT BEEN ON THE APRON; I WOULD HAVE TAXIED AROUND TO THE THRESHOLD OF RWY 17. BUT I'M CONDITIONED TO STOP AT WHITE LINES; ESPECIALLY CTLED ARPTS. WHY DIDN'T EITHER GND CTL OR THE TWR QUESTION WHY I STOPPED SHORT OF THE THRESHOLD TO RWY 17? SAFETY WAS NOT INVOLVED; BUT THE FRUSTRATION OF ONE PLT WAS. I DO NOT WANT TO TAXI ONTO AN ACTIVE RWY WITHOUT AUTH FROM THE TWR. SO I WILL CONTINUE TO STOP AT WHITE LINES. I KNOW DOUBLE WHITE LINES DENOTE THRESHOLDS; BUT I'M NOT GOING TO IGNORE A WHITE; YELLOW; PURPLE OR ANY OTHER COLOR LINE DRAWN 90 DEGS TO MY LINE OF TRAVEL. THEY ALL MEAN STOP AND ASK. BETTER TO BE SAFE THAN SORRY.