CLRED FOR AN INTXN TKOF ON RWY 31 AT DSM; PLT OF C210 STARTS TO ROLL IN WRONG DIRECTION ON RWY 13. ALERT CTLR CANCELS TKOF CLRNC AND AVOIDS A CONFLICT WITH COMMUTER ACFT LNDG ON INTERSECTING RWY.

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I CALLED TWR READY FOR TKOF AND WAS CLRED FOR TKOF FROM RWY 31 AT INTXN B. I ACKNOWLEDGED THIS CLRNC AND TAXIED INTO POS ON RWY 13 BY MISTAKE WITHOUT REALIZING IT AND ADDED TKOF PWR. AS I WAS TAXIING INTO POS I HAD NOTICED A JET LNDG ON THE INTERSECTING RWY 5 AND THOUGHT IT SOMEWHAT ODD THAT I WOULD HAVE BEEN CLRED FOR TKOF. BUT INSTEAD OF QUERYING TWR; I ASSUMED THE OTHER ACFT HAD BEEN GIVEN A LAHSO CLRNC. TWR NOTICED THE PROB AS I WAS ROUTING AND CANCELED MY TKOF CLRNC. I RETARDED THE THROTTLE AND STOPPED 2000 FT SHORT OF THE RWY INTXN. THE OTHER ACFT WAS ALSO STOPPED PRIOR TO REACHING THE INTXN. I COULD HAVE PREVENTED THIS ISSUE IN A VARIETY OF WAYS. FIRST; WITH A RWY COMBINATION OF RWY 13/31 THAT COULD EASILY BE CONFUSED. I NEED TO BE VIGILANT THAT I HEAR THE RIGHT RWY NUMBER AND TAXI ONTO THE CORRECT ONE BY CAREFUL REF TO THE DIRECTIONAL GYRO OR COMPASS. ALSO IF ANYTHING AT ALL SEEMS EVEN SLIGHTLY OUT OF THE ORDINARY; IT IS DANGEROUS TO MAKE ANY ASSUMPTIONS. IF IN DOUBT; ALWAYS ASK.