A CESSNA SKYMASTER PLT TAXIES ACROSS THE RWY HOLD LINE WITHOUT A CLRNC AT ABQ.

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THE PROB: RWY 8 IS LOCATED ABOUT 300 FT N OF THE HOLDING LINE FOR CLOSED RWY 12. I DO NOT RECALL SEEING A SIGN NOTING THAT THE HOLDING LINE AT CLOSED RWY 12 IS ALSO THE HOLDING LINE FOR RWY 8. I EXPECTED TO SEE A SEPARATE HOLDING LINE FOR RWY 8 BEYOND WHAT I THOUGHT WAS THE HOLDING LINE FOR CLOSED RWY 12. I PROCEEDED TO SLOWLY AND CAUTIOUSLY TAXI TOWARD RWY 8 WHILE LOOKING FOR ITS HOLDING LINE. NOT FINDING ONE; I STOPPED THE ACFT ABOUT 75 FT SHORT OF THE S EDGE OF RWY 8. I DID NOT INTRUDE ON RWY 8. WITHIN SECONDS OF STOPPING I WAS NOTIFIED BY GND CTL THAT I HAD CROSSED THE HOLDING LINE FOR RWY 8. GND INSTRUCTED ME TO DO A 180 DEG TURN AND BACK-TAXI TO THE HOLDING LINE WHICH I HAD PERCEIVED AS BEING EXCLUSIVE TO RWY 12. WHILE EXECUTING THE TURN AND THE BACK-TAXI ROUTINE; I APOLOGIZED TO GND AND COMMENTED ABOUT THE CURRENT GND CONDITIONS AT THE SPECIFIC SITE WHICH MAY TEND TO CONFUSE MANY PLTS NEW TO THE ARPT. NO FURTHER COMMENTS WERE MADE BY GND CTL OR MYSELF ABOUT THE EVENT; AND TWR CLRED MY ACFT FOR TKOF.