UNAUTH RWY OP ENTRY XING.

Narrative

QUITE OFTEN GND CTL WILL ONLY IDENT THE 1ST PART OF A TAXI RTE THAT THEY FEEL IS OBVIOUS. IN THIS CASE; LEAVING CONCOURSE WE UNDERSTOOD AND READ BACK: 'RWY 9R VIA PAPA.' PAPA IS THE INNER TXWY AND WOULD BE THE INITIAL RTE TO EITHER RWY 9R WITH A TURN ON TXWY T TO CROSS RWY 12 OR THE RTE TO THE RUNUP PAD FOR RWYS 12 OR 9L. OUR READBACK OF RWY 9R WAS UNCHALLENGED BY GND CTL. I QUESTIONED THE FO APCHING RWY 12 AND HE ASSURED ME THAT THE CLRNC WAS TO RWY 9R; WHICH WOULD INCLUDE ANY RWY ENRTE. I BROUGHT THE ACFT TO A 'ROLLING STOP' AND CLRED RWY 12 IN BOTH DIRECTIONS AND PROCEEDED ACROSS. JUST AS WE EXITED RWY 12 ENRTE TO RWY 9R; GND CTL ADVISED THAT WE HAD CROSSED AN ACTIVE RWY AND THAT OUR CLRNC WAS TO RWY 9L. WE INQUIRED IF THERE WAS GOING TO BE A 'PROB' AND THAT WE HAD READ BACK RWY 9R. SHE REPLIED THAT 'THERE SHOULDN'T BE A PROB' AND CLRED US TO CONTINUE TO RWY 9R. THE POINT IS THAT OUR CLRING STOP GAVE GND CTL AMPLE OPPORTUNITY TO ASSESS OUR INTENT AND THEY SAID NOTHING UNTIL IMMEDIATELY AFTER THE FACT (WAITING TO POUNCE?). A READBACK SERVES NO PURPOSE IF IT IS NOT CAREFULLY ASSESSED TO INSURE THAT A CLRNC HAS BEEN UNDERSTOOD. SUPPLEMENTAL INFO FROM ACN 309641: WHILE TAXIING FROM THE RAMP I CALLED GND FOR TAXI. DURING THIS SHORT TAXI ACROSS RWY 12; WE HAD JUST STARTED BOTH ENGS; RAN THE BEFORE TAXI CHKLIST. WE WERE GOING THROUGH THE BEFORE TKOF CHKLIST WHEN I CALLED GND. I SHOULD HAVE WAITED ON THE BEFORE TKOF CHKLIST UNTIL TALKING WITH GND. I WAS DOING SEVERAL THINGS AT ONCE AND JUST GLANCED QUICKLY AT THE TAXI CHART INSTEAD OF TAKING A GOOD LOOK. WE WERE RUSHED BECAUSE WE WERE 20 MINS LATE. WE SHOULD NEVER HAVE LET THAT PUT US IN THAT POS. WE SHOULD HAVE VERIFIED WITH ATC THAT WE WERE CLRED TO CROSS A RWY TO ANOTHER RWY.