UNAUTH RWY XING ENTRY OP.

Narrative

WHILE TAXIING OFF RWY 31R ONTO TXWY 18; WE RECEIVED INSTRUCTIONS TO CROSS RWY 35R; TURN L ON LIMA; AND CONTACT GND CTL. BEING UNFAMILIAR WITH THAT AREA OF THE ARPT; I LOOKED DOWN AT THE ARPT DIAGRAM. THE CAPT ASKED FOR THE AFTER LNDG CHKLIST AND IF WE WERE CLRED TO CROSS. NEITHER OF US UNDERSTOOD THE CLRNC COMPLETELY. I ASKED THE TWR TO 'SAY AGAIN' AT LEAST 1 MORE TIME AND IT MAY HAVE BEEN TWICE. SINCE WE WERE ALREADY XING RWY 35R; WE HEARD CLRED TO CROSS AGAIN ('ANTICIPATING' 35L) AND STILL LOOKING FOR TXWY LIMA. WHEN WE FOUND OURSELVES AT KILO; WE BOTH REALIZED THAT LIMA WAS BEHIND US AND THE RWY WE HAD JUST CROSSED WAS AN ACTIVE RWY WITHOUT CLRNC. OTHER FACTORS: NEITHER THE CAPT NOR I HAD BEEN IN THAT AREA OF THE ARPT BEFORE. IT WAS THE CAPT'S FIRST LNDG IN THAT TYPE OF ACFT. I AM A LOW-TIME FO IN THAT TYPE OF AIRPLANE. ANTICIPATION -- NORMALLY WHEN TOLD TO SWITCH TO GND CTL AT MOST ARPTS; YOU ARE CLRED TO CROSS ACTIVE RWYS. SUPPLEMENTAL INFO FROM ACN 260235: I DID NOT KNOW WHERE 'LIMA' WAS AND ASKED COPLT. HE WAS LOOKING UP MAPS AND DOING AFTER LNDG CHKLISTS AND DID NOT ANSWER. I LOOKED FOR LIMA SIGN BUT DID NOT SEE ONE. AN ACFT WAS ON SHORT FINAL FOR RWY 35R SO I WAS TRYING TO HUSTLE A HVY SHIP ACROSS AND PROBABLY MISSED THE LIMA SIGN BTWN RWY 35R/35L (I ASSUME IT'S THERE). WE RECEIVED CLRNC AGAIN TO TURN L ON LIMA -- NOW I HAD A MINDSET IT WAS ON THE OTHER SIDE OF RWY 35L. WE BOTH LOOKED AND SAW NO ACFT ON RWY 35L AND CONTINUED ACROSS. I ALSO THOUGHT THAT BECAUSE WE WERE ON GND; HE HAND CROSSED US. IT ALSO WAS MY FIRST LNDG AFTER TRAINING IN THIS CRAFT. I WAS ALSO TRYING TO ADJUST MY COCKPIT LIGHTS (WHICH I COULD NOT FIND). I SHOULD HAVE STOPPED THE MOMENT I WAS NOT ABSOLUTELY SURE OF THE CLRNC. ALTHOUGH WE HAD TAXI MAPS HANDY; LIMA WAS NOT EASILY APPARENT TO US. I BELIEVE I HEARD WHAT I EXPECTED; 'CROSS 35L;' NOT WHAT THE CTLR SAID; BECAUSE IT WAS THE SECOND OR THIRD CLRNC TO CROSS.