ACR TAXIED PAST HOLD LINE FOR ACTIVE RWY. PLTDEV. POTENTIAL CONFLICT.

Narrative

ON FIRST FLT OF THE DAY IN THE HOLD SHORT BLOCKS WITH 2 OTHER ACFT. FROM OUR POS IT LOOKED LIKE WE WERE #2 TO DEPART. I WAS CONCERNED WITH THE WX AS THERE WERE SOME TSTMS AROUND AND IT WAS THE FO'S LEG. I WAS ALSO GOING OVER THE DEP PROCS FOR DCA AND CHKING THE WX RADAR PICTURE WHEN WE WERE CLRED UP TO AND HOLD SHORT OF RWY 36 AND TOLD WE ARE NEXT TO GO. AS I WAS PREOCCUPIED AND SURPRISED BY THE CALL THAT WE WERE NEXT TO GO; I THOUGHT WE WERE CLRED FOR TKOF AND WAS PROCEEDING ONTO THE RWY WHEN THE FO APPLIED THE BRAKES JUST AFTER XING THE HOLD LINE. HE THEN SAID WE WERE ONLY CLRED TO HOLD SHORT AS THERE WAS ACR Y ON ABOUT A 3 MI FINAL. THERE WAS MUCH TO THINK ABOUT ON A TKOF SUCH AS THIS. SIMPLER DEP PROCS AND A VISUAL SIGNAL LIGHT (I.E.; RED OR GREEN) PRIOR TO RWY ENTRY POINTS WOULD HELP PREVENT SUCH OCCURRENCES. I WAS WEARING A HEADSET AT THE TIME AND THERE WERE NO RADIO PROBLEMS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: TALKED WITH RPTR REF HIS PARTICIPATION IN RWY INCURSION STRUCTURED CALLBACK PROGRAM. HE HAS PRETTY HECTIC SCHEDULE AND ASKED TO BE EXCLUDED. RPTR CLARIFIED TYPE ACFT. SAID THAT THERE WAS NOT A SERIOUS RWY INCURSION AS HIS COPLT JUMPED ON BRAKES BEFORE THEY GOT ONTO RWY. ACFT LNDG HAD NO PROBLEM.