CL65 FLC FOLLOWED THE WRONG TXWY OUT AND TOOK OFF WITHOUT CLRNC.

Narrative

WE HAD BEEN CLRED TO TAXI FROM SPOT X VIA TXWY WB TO TXWY WC IN IAH. AFTER LOOKING AT THE CHART AND THE SIGNS MARKING THE TXWYS; I FOLLOWED WHAT I THOUGHT WAS TXWY WB ONLY TO FIND MYSELF ON TXWY WA. THE SIGNS IN IAH ARE NOT LABELED CLRLY AND THIS IS NOT THE FIRST TIME I HAVE TAKEN THE WRONG ROAD. WITH MY JOB I WILL FLY INTO IAH A COUPLE OF TIMES IN A MONTH AND THEN NOT AGAIN FOR ANOTHER YR; WHICH DOES NOT BREED FAMILIARITY. THE SIGNS NEED ADDITIONAL ARROWS AND BETTER IDENT FOR CLARIFICATION. ON THIS SAME TRIP; AS WE STARTED OUR TKOF ROLL IN IAH; THE CTLR CAME ON AND CLRED ACR X FOR TKOF ON RWY 15R. BOTH MYSELF AND MY FO UNDERSTOOD THAT WE HAD ALREADY BEEN CLRED FOR TKOF. I QUERIED THE CTLR AND HE SAID THAT HE WAS PRETTY SURE THAT HE HAD ONLY CLRED US INTO POS AND HOLD. FORTUNATELY; THE TFC WAS LIGHT AND THERE WERE NO CONFLICTS. THE FO AND I WERE BOTH EXHAUSTED AFTER DEALING WITH WX AND MECHANICALS FOR 2 DAYS SO SEVERAL MISTAKES WERE MADE. IT MAY BE POSSIBLE THAT WE MISUNDERSTOOD; OR HEARD THE TKOF CLRNC WE WERE EXPECTING. WITH MY FO BEING TOTALLY UNFAMILIAR WITH IAH AND MYSELF BEING ONLY SLIGHTLY FAMILIAR; THE TXWY INCURSION COULD HAVE BEEN AVOIDED IF THE TXWYS WERE ADEQUATELY LABELED. SUPPLEMENTAL INFO FROM ACN 556733: UPON REACHING THE DEP RWY; TWR ISSUED US A 'CLRED FOR TKOF.' I READ BACK CLRED FOR TKOF AND COMPLETED THE CHKLIST. THE CAPT GAVE ME CTL OF THE ACFT AND WE BEGAN THE TKOF ROLL. BEFORE ROTATION; TWR AGAIN SAID CLRED FOR TKOF. WHILE CLBING OUT; WE ADVISED TWR OF OUR UNDERSTANDING OF A PRIOR TKOF CLRNC; BUT THEY DID NOT COMMENT. NO CONFLICTS EXISTED AND NO MORE WAS SAID.