MD80 FLT CREW EXIT ON UNCHARTED TXWY AFTER LNDG TUS RWY 29R. ATC INFORMED CREW THAT NEWLY CONSTRUCTED TXWY NOT STRESSED FOR ACFT TYPE.

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DURING ROLLOUT AT TUS ON RWY 29R AT NIGHT; WE WERE INSTRUCTED TO MAKE A R TURN ON EITHER A7 OR A6. WE WERE TRAVELING TOO FAST TO MAKE A7 AND CONTINUED TO THE NEXT CHARTED TXWY WHICH WE THOUGH WAS A6. AS WE MADE THE TURN; WE DISCOVERED THAT WE WERE NOT ON A6; BUT INSTEAD ON AN UNCHARTED TXWY TANGO. TWR INFORMED US THAT TANGO WAS NOT STRESSED FOR MD80 ACFT. WE WERE AT A POINT WHERE WE COULD NOT POSSIBLY TURN; AND STOPPING ALSO CONCERNED ME BECAUSE OF THE POSSIBILITY OF THE ACFT SETTLING. I ELECTED TO EXPEDITIOUSLY TAXI CLR OF TXWY TANGO ONTO TXWY ALPHA. I CALLED THE TWR ON THE PHONE AFTERWARDS AND WAS ADVISED THAT NO DAMAGE WAS DONE TO TXWY. THEY ALSO ADVISED ME THAT TXWY TANGO HAD BEEN IN EXISTENCE FOR APPROX 90 DAYS. TXWY TANGO DOES NOT APPEAR ON THE CURRENT COMMERCIAL CHARTS NOR IS THERE ANY MSG OR REFERENCE TO IT IN THE FIELD CONDITION RPT. ALSO; THE ONLY PROHIBITED TXWYS LISTED ON THE 10-7 PAGE ARE A5 AND C. I DO NOT BELIEVE; THAT HAD THIS DATA BEEN AVAILABLE TO US; THIS OPERROR WOULD HAVE OCCURRED. SUPPLEMENTAL INFO FROM ACN 595240: DURING LNDG ROLL OUT AT ABOUT 110 KTS TWR INSTRUCTED US TO TURN R ON EITHER A7 OR A6. IT SHOULD BE NOTED THAT DECEL CALLOUTS WERE STILL IN PROGRESS AND LNDG WAS AT NIGHT SO PRIMARY ATTENTION WAS FOCUSED ON THE LNDG ROLLOUT. AFTER A QUICK DISCUSSION AND OBSERVATION THAT THE TXWY WAS CONCRETE; AND GIVEN THAT THERE WAS NO ROOM FOR A TURN; CAPT DECIDED TO EXPEDITIOUSLY CLEAR THE RWY AS THE MOST PRUDENT COURSE OF ACTION.