PLT OF AN ATX CARGO BEECH B58 BARON; INADVERTENTLY TAXIED ONTO AN ACTIVE RWY DURING TAXI OUT.

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TAXIING BEYOND HOLD SHORT AREA PROB AROSE AFTER 3 SEPARATE TAXI INSTRUCTIONS WERE GIVEN TO MY ACFT AT CAPITOL ARPT (SPI). MY ACFT LEFT FBO HANGAR WITH CARGO AND AN IFR CLRNC AND A TAXI CLRNC TO TXWY A8 INTXN DEP RWY 22. TAXIING ENRTE TO TXWY A8 INTXN; MY ACFT WAS GIVEN ANOTHER TAXI CLRNC TO INTXN D RWY 22 DEP. AFTER ACCEPTING NEW CLRNC AND TAXIING IN THAT DIRECTION; A THIRD CLRNC WAS GIVEN AND ACCEPTED TO TAXI TO RWY 13 INTXN D DEP. NO HOLD SHORT INSTRUCTIONS WERE GIVEN. THIS IS A VERY LARGE INTXN CAPABLE OF DEPARTING ON 4 DIFFERENT RWYS; ALSO WITH ACCESS TO TXWYS. THE HOLD SHORT LINE FOR RWY 13 IS ALSO THE HOLD SHORT LINE FOR RWY 22 WITH NO HOLD SHORT CLRNC GIVEN; I TAXIED TOWARD RWY 22 TO LINE UP ON AND REMAIN OFF OF THE ACTIVE RWY 13. INSTANTLY REALIZING I WAS PAST THE STOP LINE; I MADE A 180 DEG TURN OFF OF RWY 22 AND BACK TO THE STOP LINE. AT THE SAME TIME; I MADE THE TURN BACK TO THE STOP LINE; GND CTL ADVISED ME OF THE SAME. ANOTHER AIRPLANE HAD BEEN CLRED FOR THE TKOF AT THE FAR END OF RWY 13. HE HAD NOT STARTED HIS TKOF ROLL. I FLY OUT OF MANY AND MUCH LARGER ARPTS AND THIS IS PROBABLY THE LARGEST AND MOST CONFUSING INTXN I'VE SEEN. SINCE THIS PROB AROSE; I HAVE MADE CONTACT WITH BOTH ATC MGRS AND MR X AT THE SPRINGFIELD FSDO ON THIS MATTER. THEY ALL AGREE THIS IS A CONFUSING INTXN. I WAS ALSO TOLD BY ONE OF THE ATC MGRS THE INTXN IS SCHEDULED TO BE REMADE FOR THIS REASON BUT NOT FOR ANOTHER YR.