FOLLOWING BEING VECTORED OFF THE SID; MD80 FLT CREW MISINTERPRETS DEP CTL INSTRUCTION TO RESUME THE NOBLY SID LIT TRANSITION.

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UNINTENTIONALLY DEVIATED FROM THE NOBLY RNAV DEP FROM DFW ARPT. THE FO AND I BOTH COPIED A NEW CLRNC AND I ENTERED IT INTO THE FMS. WE HAD ORIGINALLY BEEN ASSIGNED THE FERRA DEP WITH CDS TRANSITION AND FURTHER CLRNC TO IRW AND TUL; OUR DEST; DUE TO TSTMS IN THE VICINITY OF DFW. AS WE PULLED UP TO DFW RWY 18L FOR DEP; TWR ANNOUNCED THAT ALL W DEPS WERE JUST CLOSED OFF. I ASKED THE FO TO CHK WITH DFW CLRNC TO SEE IF WE COULD CHANGE TO THE DEP UP TO MLC SINCE WE REALLY WERE NOT GOING W. CLRNC SAID WE WOULD HAVE TO TAKE AN E DEP AND WE AGREED THAT WOULD WORK. I UNDERSTOOD THE CLRNC TO BE THE NOBLY DEP TO LIT DIRECT RZC AND DIRECT TUL AND ENTERED IT INTO THE FMS WITH THE LITTLE ROCK TRANSITION. IMMEDIATELY AFTER CONTACTING REGIONAL DEP CTL WE WERE ASSIGNED HDG 153 DEGS AND TAKEN OFF THE DEP AND TOLD WE COULD ACCELERATE TO 250 KIAS. WE RECEIVED A FURTHER TURN TO THE L. I THINK A HDG OF 090 DEGS WAS ASSIGNED AND AFTER A SHORT TIME TOLD TO RESUME THE DEP TO NOBLY AND I THOUGHT AT THAT TIME DIRECT LIT AFTER NOBLY. I THINK THE FO THOUGHT THE SAME THING AND WE SET UP THE FMS FOR DIRECT TO LIT AFTER NOBLY. A VERY SHORT TIME AFTER PASSING NOBLY; ZFW CALLED AND ASKED IF WE WERE STILL ON THE DEP AND WE RESPONDED THAT WE WERE GOING DIRECT LIT. THE CTLR SAID WE WERE STILL SUPPOSED TO BE ON THE LIT TRANSITION TO LIT; NOT DIRECT TO LIT. WE REENTERED THE FULL NOBLY DEP AND CORRECTED BACK TO THE COBUG FIX. THERE DID NOT APPEAR TO BE ANY TFC CONFLICT AT THE TIME AND I DON'T THINK WE WERE VERY FAR L OF COURSE BUT WE HAD SELECTED LIT INTENTIONALLY BECAUSE THAT WAS WHAT WE THOUGHT WAS INTENDED AT THE TIME. IT HAD ALREADY BEEN A FAIRLY LONG DAY AND THE FO AND I WERE BOTH PROBABLY SOMEWHAT TIRED WHICH MAY HAVE CONTRIBUTED TO OUR MISTAKE.