ATCT LCL CTLR AT TPA CLRED TWO ACFT TO DEPART RWY 18R WITH AN MD80 STOPPED AND NOT COMPLETELY CLR OF RWY.

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WE WERE GIVEN A CLRNC TO TAXI TO RWY 18R FOR DEP AT TPA. TXWY 'W' WAS CLOSED FROM S OF W6 TO W3 WHICH MEANT THAT WE HAD TO TAXI ON THE RAMP TO A6. ALSO THE RUNUP BLOCK AREA WAS PARTIALLY CLOSED SO AS TO ONLY HAVE SPACE FOR ONE ACFT AT A TIME ACCESS TO THE RWY. AS WE APCHED THE 'NUMBER ONE' POS FOR TAKEOFF; WE HAD YET TO RECEIVE OUR WEIGHT AND BALANCE INFORMATION. A COMPANY ACFT AHEAD WAS RETURNING TO THE GATE AND WE VOLUNTEERED TO GET OUT OF THE WAY BY TAXIING DOWN THE RWY 18R. WE WERE CLRED TO TAXI DOWN RWY 18R EXIT W6 AND GIVE WAY TO ACFT Z MD 80 ON W. AS WE CLRED THE RWY; ACFT Z STOPPED S OF W6 TO SEE WHAT WE WERE DOING AND THE TWR CLRED A DHC-8 COMMUTER FOR TKOF FROM RWY 18R. I REALIZED AT THAT TIME THAT ALTHOUGH WE WERE CLR OF THE RWY; PART OF OUR ACFT WOULD BE OVER THE HOLD SHORT LINE IN ORDER TO KEEP 'W' CLR. AS ACFT Z CLRED W6 I WAS UNSURE IF THE TWR WANTED US TO GO N OR S ON 'W' AND BY THEN AN ACFT B B737 WAS CLRED TO TAKE OFF ON RWY 18R. AFTER TKOF THE ACFT B PLT CALLED THE TWR TO REPORT THAT ACFT X MIGHT WANT TO PULL A LITTLE FURTHER OFF THE RWY NEXT TIME. I MISTAKENLY BELIEVED THE TWR WAS WATCHING THE SITUATION AND WOULDN'T CLR ANYONE FOR TAKEOFF UNTIL WE HAD TIME TO CLR. I SHOULD HAVE IMMEDIATELY CALLED THE TWR TO LET HIM KNOW WE MIGHT NOT BE ALL THE WAY CLR OF THE RWY. CONTRIBUTING FACTORS WERE THE CONSTRUCTION ON THE ARPT; AND ALSO THE GREAT WEATHER. THE GREAT WEATHER CREATED A MINDSET THAT ALL PARTIES COULD SEE WHAT WAS GOING ON. THE NEXT TIME I EXIT AN ACTIVE RWY IN AN UNUSUAL CIRCUMSTANCE; I WILL PAY VERY CLOSE ATTENTION TO HOW MUCH ROOM I HAVE TO EXIT AND COMMUNICATE ANY DOUBTS I MIGHT HAVE IN A TIMELY MANNER. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR SAID HALF OF THE RWY 18R RUNUP AREA WAS CLOSED. HE SAID THEY WERE WAITING FOR WEIGHT AND BALANCE INFORMATION AND TFC BEHIND THEM COULD NOT GET BY FOR TAKEOFF. THE TWR CTLR INSTRUCTED THE FLIGHT TO TAXI DOWN THE RWY AND EXIT AT THE FIRST INTERSECTION; HALF OF WHICH WAS ALSO CLOSED.