DURING A NIGHT LNDG ROLL ON RWY 18R AT CVG; A B757 AT 100 KTS IS ASKED TO EXIT AT TXWY J OR TXWY K. ASSUMING THE UPCOMING 2 LIGHTED TXWYS WERE THE CORRECT ONES; A TURNOFF WAS MADE AT TXWY D4. A TKOF CLRNC WAS CANCELED ON RWY 27 AND THE FOLLOWING ACFT FOR LNDG RWY 18R HAD LNDG CLRNC CANCELED.

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ON LNDG ON RWY 18R AT APPROX 100 KTS; TWR ASKED IF WE COULD MAKE TXWY J OR TXWY K. WE SAW 2 (ONLY) TXWYS LIT UP WITH GREEN TAXI CTRLINE LIGHTS. ONE WAS ON ONE SIDE OF RWY 27 AND THE OTHER WAS PAST RWY 27. WE SAID WE COULD MAKE ONE OF THESE 2 GREEN LIT TXWYS. SINCE WE WERE HVY AND HAD A HIGH APCH SPD; WE CROSSED RWY 27 AND TOOK THE SECOND TXWY. WHAT THE TWR WANTED WAS FOR US TO HOLD SHORT OF RWY 27 SO THEY COULD USE IT FOR A TKOF. WE COULDN'T REFER TO THE TAXI CHART ON THE RWY AT 100 KTS AND WRONGLY ASSUMED THAT THE TXWYS THEY WANTED US TO MAKE WERE THE LIT GREEN ONES. IF THEY HAD ASKED US IF WE COULD HOLD SHORT OF RWY 27; THAT WOULD HAVE CLARIFIED THE WHOLE SIT. IF THEY HAD ASKED US IN THE AIR; IT WOULD HAVE BEEN EVEN BETTER. THEIR ATTEMPT TO COMPLETE TOO MANY OPS CREATED AN UNSAFE OP. LAHSO'S ARE NO LONGER ALLOWED ON THAT RWY AND THEY WERE TRYING TO DO IT 'UNDER THE TABLE.' SUPPLEMENTAL INFO FROM ACN 577059: TWR REQUESTED US TO TURN OFF AT EITHER TXWY J OR TXWY K AND ASKED IF WE COULD MAKE EITHER ONE. WE SAID YES (AS WE WERE LOOKING AT 2 HIGH SPD GREEN TURNOFF SETS OF LIGHTS). WE WERE TOO FAST FOR THE FIRST ONE; SO WE DECIDED TO TAKE THE NEXT TURNOFF. TWR DID NOT 'TELL' US TO HOLD SHORT OF RWY 27 AT ANY TIME. THEY 'EXPECTED' US TO HOLD SHORT OF RWY 27 WITH AN EARLY TURNOFF. CONSEQUENTLY; THEY CANCELED A TKOF CLRNC ON RWY 27; AND HAD THE ACFT BEHIND US ON RWY 18R GO AROUND. CALLBACK CONVERSATION WITH RPTR ACN 577057 REVEALED THE FOLLOWING INFO: THE OTHER ACFT INVOLVED WERE A CRJ ON FINAL FOR RWY 18R AND AN UNDEFINED MODEL MCDONNELL DOUGLAS ON RWY 27. CANCELLATION OF BOTH THE LNDG AND TKOF CLRNC WAS DONE IN A TIMELY MANNER WITH NO CONFLICT RESULTING. THE TOUCHDOWN POINT WAS AT THE NORMAL POINT; BUT THE LNDG WAS PLANNED WITH MINIMUM USE OF BRAKING AND REVERSE THRUST DUE TO ECONOMIC CONSIDERATIONS. DURING FOLLOW-UP WITH THE TWR; IT WAS LEARNED THAT LAHSO IS NOT AUTH; SO THE REQUEST FOR A TURNOFF TO BE MADE ON THE MENTIONED TXWYS IS TO AVOID THE APPEARANCE OF LAHSO BY USING THE RWY 27 DESIGNATION. THE CLRNC DURING THE LNDG ROLL AS IT WAS GIVEN WAS CONFUSING; BUT ACCORDING TO THE RPTR; WOULD HAVE BEEN MORE PRECISE AND LESS CONFUSING IF THE RWY WOULD HAVE BEEN MENTIONED. KNOWING THEN THE PRECISE DESIRE OF THE TWR; THE REQUEST WOULD HAVE BEEN REFUSED BECAUSE OF THE ORIGINAL LNDG ROLLOUT PLAN IN THIS INSTANCE.