ACR TAXIES ACROSS ACTIVE RWY WITHOUT CLRNC.

Narrative

WHILE IN TAXI TO DEPART FROM XYZ; OUR FLT WAS TOLD TO TAXI TO RWY 19R VIA TXWYS B; M; AND E; WITH NO OTHER RESTRS. AS CAPT; I HEARD THE INSTRUCTIONS AND REPEATED THEM TO THE FO. HOWEVER; AFTER TURNING ONTO TXWY M; WE FINISHED THE BEFORE TKOF CHKLIST; CLRED OURSELVES VISUALLY L AND R; AND CROSSED RWY 19R ON OUR WAY TO RWY 25L (INSTEAD OF MAKING THE L TURN UP TXWY E FOR THE CORRECT RWY). THE CTLR NOTICED OUR MISTAKE AND INFORMED US TO CONTINUE STRAIGHT AHEAD FOR A DEP ON RWY 25L. ANY NUMBER OF CHANGES COULD HAVE PREVENTED THIS OCCURRENCE. 1) EITHER ONE OF THE FLC NOTICING THE MISTAKE AS WE STARTED TO CLR OURSELVES ACROSS RWY 19R. 2) SLIGHTLY DIFFERENT TAXI RTE FOR RWY 19R (TXWYS B; G; AND E) SO AS TO AVOID TXWY M WHICH LED TO THE OTHER ACTIVE RWY FOR THE DAY (RWY 25L). 3) NOT USING 2 DIFFERENT DIRECTIONAL RWYS FOR ARR AND DEP (WE LANDED ON RWY 25L 30 MINS EARLIER). 4) IF WE HAD LANDED ON RWY 19R WE WOULD HAVE BEEN IN THE MINDSET TO DEPART ON THE SAME RWY. HOWEVER WE LANDED ON RWY 25L. SUPPLEMENTAL INFO FROM ACN 451920: IN DISCUSSING OUR ERROR; THE CAPT SAID HE WAS DISTR AS I REPEATED TAXI INSTRUCTIONS AS WE WERE BEING MARSHALLED OUT OF THE GATE. SINCE WE JUST PREVIOUSLY LANDED ON RWY 25L HE WAS UNDER THE IMPRESSION WE WERE TO TAXI TO RWY 25L. AS WE WERE TAXIING; I JUST COMPLETED READING A CHKLIST AS WE TAXIED ONTO THE RWY. THE CAPT SAID CLR L; AND JUST THEN I LOOKED UP TO CLR THE R SIDE WHEN I REALIZED WE WERE ON THE RWY. WE EXITED THE RWY AND LUCKILY THERE WAS NO TFC CONFLICTS.