PLTDEV WHEN COMMUTER BE02 CROSSED THE ACTIVE RWY WHILE AN MD80 WAS ON TKOF ROLL. THE MD80 ABORTED. THE LCL CTLR HAD PUT A COMPANY ACFT WITH A SIMILAR CALL SIGN TO THE COMMUTER IN POS ON THE SAME RWY AS THE MD80.

Narrative

ACR X WAS CLRED FOR TKOF. ACR Y WAS PUT INTO POS AND HOLD (BOTH ON RWY 34R) WITH A FURTHER STATEMENT OF 'AT THE S END.' ACR Z WAS APCHING INTXN Q; NOT TALKING TO ME AND CROSSED THE RWY WITHOUT AUTH BY ME. ACR X ABORTED HIS DEP. I FEEL THAT 3 PEOPLE MISSED THE READBACK BY ACR Z. HOWEVER; SIMILAR SOUNDING CALL SIGNS AND THE PLT NOT LISTENING TO THE XMISSION CONFIRMING THAT HE WAS AT INTXN Q AND NOT AT THE S END. ACR Z HAD ALREADY BEEN ALMOST CLR OF RWY 34 BTWN THE RWYS WHEN ACR X HAD STOPPED. SUPPLEMENTAL INFO FROM ACN 374635: THE CREW OF ACR Z WAS INSTRUCTED BY SEA GND TO TAXI TO RWY 34R AT INTXN Q. I WAS THE CAPT TAXIING THE ACFT AND THE FO PERFORMED THE DUTIES OF THE CHKLIST AND RADIO CALLS. WE HAD JUST COMPLETED OUR PREFLT CHKS AS WE APCHED INTXN Q. THERE WERE SEVERAL ACFT AT THE APCH END OF RWY 34R INCLUDING ACR Y WHO WAS AT THE HOLD SHORT LINE OF RWY 34R FULL LENGTH. THE FO RESPONDED TO A RADIO CALL FROM SEA TWR; 'ACR Z CLRED POS AND HOLD RWY 34R AT INTXN Q.' SEA TWR DID NOT RESPOND TO THIS. I (THE CAPT) BEGAN TAXIING THE ACFT ONTO THE RWY AT INTXN Q. I VISUALIZED APPARENT MOVEMENT FROM AN ACR X MD80. I PWRED THE ACFT ACROSS RWY 34R TO THE HOLD SHORT LINES OF RWY 34L; BTWN THE 2 RWYS CLR OF BOTH RWYS. ACR X RESPONDED TO SEA TWR THAT THEY WERE ABORTING THE TKOF; AND WERE INSTRUCTED BY SEA TWR TO CLR THE RWY. THE FO QUERIED SEA TWR VERIFYING ACR Z CLRED INTO POS AND HOLD RWY 34R AT INTXN Q. THE SEA TWR DID NOT RESPOND. A DIFFERENT CTLR CAME ON THE RADIO AND CLRED ACR Y FOR TKOF ON RWY 34R AND THEN CLRED OUR ACFT (ACR Z) FOR TKOF ON RWY 34L. NOTHING ELSE WAS SAID. SUPPLEMENTAL INFO FROM ACN 374636: TWR CLRED AN ACFT FOR 'POS AND HOLD RWY 34R.' I RESPONDED THIS CALL WITH 'ACR Z POS AND HOLD RWY 34R AT INTXN Q.' THE TWR DID NOT RESPOND. FACTORS CONTRIBUTING TO THIS SIT WERE SIMILAR CALL SIGNS AND ATC'S FAILURE TO MONITOR READBACKS AND THE RWY ENVIRONMENT. ACR Z AND ACR Y HAD 3 NUMBERS IN COMMON IN SEQUENCE. IN ADDITION MY CREW HAD PREVIOUSLY FLOWN; THAT; DAY; NUMBERS 1234; 1235; AND 1236. THIS WAS A FACTOR IN ME RESPONDING TO THE CALL SIGN. THE FAILURE OF ATC TO MONITOR MY READBACK OF THEIR INSTRUCTIONS WAS ALSO A FACTOR.