DISTRS AND CONFUSION CAUSED BY RAAS WARNING RESULT IN REJECTED TKOF.

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AS WE TAXIED OUT FOR TKOF THERE WERE QUITE A FEW PLANES LINED UP FOR TKOF WITH A LOT OF LNDG TFC FOR BOTH RWY 16C AND L. WHEN IT WAS OUR TURN FOR DEP WE WERE INITIALLY CLRED TO TAXI INTO POS AND HOLD ON RWY 16L. AFTER I HAD ALREADY CROSSED THE RWY HOLD SHORT LINE RAAS MADE AN ADVISORY 'APCHING 16L.' I CONTINUED WITH MY LINE-UP ON RWY 16L AND JUST AS THE PLANE WAS LINED UP WITH THE DEP RWY ATC INSTRUCTED 'FLT NUMBER CLRED FOR TKOF RWY 16L' JUST AS THE DEPARTING AIRPLANE IN FRONT OF US WAS ROTATING. I ASKED THE FO TO COMPLETE THE TKOF CHKLIST AND THEN XFERRED CTL OF THE ACFT TO HIM AND OUR TKOF ROLL STARTED. IT SHOULD BE NOTED AS SOON AS THE AIRPLANE WAS JUST LINING UP WITH THE CTRLINE OF RWY 16L RAAS ANNOUNCED 'ON RWY 16L.' THE FO ADVANCED THE THROTTLES AND STARTED THE TKOF ROLL AS I MADE MY REQUIRED NON-FLYING CALLS. AS WE ACCELERATED TO APPROX 20 KTS I HEARD SEATTLE TWR ISSUE A CLRNC STATING 'CLRED TO CROSS RWY 16L' AND I IMMEDIATELY ABORTED THE TKOF THINKING PERHAPS THE CLRNC WAS FOR ONE OF THE ACFT THAT HAD JUST LANDED ON RWY 16C. WE NEVER HEARD ANY OTHER COM OTHER THAN 'CLRED TO CROSS RWY 16L.' AS WE EXITED THE RWY FROM ABOUT A 20 KT ABORT SPD ATC QUERIED US FOR THE REASON FOR OUR ABORT. AFTER INFORMING THEM OF OUR ABORT REASON; ATC STATED EVERYONE HAD BEEN INSTRUCTED TO HOLD SHORT OF RWY 16L; YET AS WE REACHED THE DEP END OF RWY 16L FOR OUR NEXT TKOF ATTEMPT ATC ADVISED US THAT THEY HAD CLRED AN ACFT BEHIND US ACROSS RWY 16L. ENRTE THERE WAS MUCH CONFUSION ON MY PART; AS WELL AS MY FO'S OVER WHY WE DID NOT HEAR OTHER INSTRUCTIONS ATC CLAIMED TO HAVE ISSUED. AFTER LNDG; I MADE A CALL TO SEA TWR IN AN EFFORT TO TRY AND CLARIFY WHAT WENT WRONG AND CAUSED OUR ABORTED TKOF. ACCORDING TO SEATTLE TWR; AFTER WE HAD BEEN ISSUED A TKOF CLRNC; TWR ASKED A FLT BEHIND US IN LINE FOR TKOF IF THEY COULD ACCEPT RWY 16C. AFTER THE FLT BEHIND US SAID THEY COULD ACCEPT RWY 16C; THEY WERE INSTRUCTED TO CROSS RWY 16L BEHIND US AFTER WE HAD BEEN CLRED FOR TKOF. THIS INFO REALLY BOTHERED ME EVEN MORE AS I COULDN'T UNDERSTAND WHY WE DIDN'T HEAR ANY OF THIS COM ON TWR FREQ. AFTER DISCUSSING THIS MATTER WITH ANOTHER PLT; I BELIEVE NOW WHAT MOST LIKELY HAPPENED WAS THAT RAAS INTERRUPTED AN ATC INSTRUCTION TO THIS FLT BEHIND US AND NEITHER ME OR MY FO HEARD THE 'REST OF THE STORY.' HAD I KNOWN 'THE REST OF THE STORY' I WOULD NOT HAVE REJECTED OUR TKOF AS I DID THINKING A PLANE DOWNFIELD OF US WAS ABOUT TO CROSS OUR DEPARTING RWY. ALSO; I'VE SEEN SEATTLE TWR CLR FLTS ACROSS RWY 16L FOR DEP ON RWY 16C QUITE A BIT IN THE EARLY MORNINGS; BUT NEVER AT THE TIME OF DAY WE WERE DEPARTING SO THIS CLRNC FOR THE FLT BEHIND US WASN'T SOMETHING I WAS EXPECTING TO HEAR. RAAS NEEDS TO GO! PERIOD! I BELIEVE IT CREATED A SERIOUS PROB BY BLOCKING ATC COMS AT A CRITICAL PHASE OF FLT. IT'S MY BELIEF THAT A MOVING MAP SYS OF THE ARPT DIAGRAM; PERHAPS DISPLAYED ON THE LOWER DU WHERE HYD INFO IS DISPLAYED WOULD BE A MUCH MORE USER-FRIENDLY AND SAFE TOOL FOR SITUATIONAL AWARENESS THAN RAAS IS.