Narrative:

Runway 23 in use at tys. Threshold for runway 23L is displaced for construction, 5200 ft. Taxiway A4 is used for departures on runway 23L. Aircraft X, C150, landed on runway 23L; and is rolling out to the end of the runway. I put aircraft Y, maule, in position and hold on runway 23L while aircraft X was rolling out. When it appeared aircraft X was turning left off runway 23L, I cleared aircraft Y for takeoff on runway 23L. When aircraft Y was about 1000 ft down the runway on takeoff roll, I saw aircraft X taxiing northeast. It appeared aircraft X was on the runway, so I canceled takeoff clearance for aircraft Y and asked ground control to verify aircraft X is on taxiway a. Ground control confirmed aircraft X was on taxiway a and I reclred aircraft Y. Our tower is so low I'm not able to differentiate between aircraft on the runway or taxiway. This is a continuing problem at tys with most incidents not being reported. The best solution would be a taller tower. Next may be some type of ground detection equipment and/or video camera at strategic locations.

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Original NASA ASRS Text

Title: TYS LCL CTLR CANCELS TKOF CLRNC ON DEPARTING MAULE DUE TO VISUAL PERCEPTION THAT LNDG C150 HAD NOT TURNED OFF THE RWY.

Narrative: RWY 23 IN USE AT TYS. THRESHOLD FOR RWY 23L IS DISPLACED FOR CONSTRUCTION, 5200 FT. TXWY A4 IS USED FOR DEPS ON RWY 23L. ACFT X, C150, LANDED ON RWY 23L; AND IS ROLLING OUT TO THE END OF THE RWY. I PUT ACFT Y, MAULE, IN POS AND HOLD ON RWY 23L WHILE ACFT X WAS ROLLING OUT. WHEN IT APPEARED ACFT X WAS TURNING L OFF RWY 23L, I CLRED ACFT Y FOR TKOF ON RWY 23L. WHEN ACFT Y WAS ABOUT 1000 FT DOWN THE RWY ON TKOF ROLL, I SAW ACFT X TAXIING NE. IT APPEARED ACFT X WAS ON THE RWY, SO I CANCELED TKOF CLRNC FOR ACFT Y AND ASKED GND CTL TO VERIFY ACFT X IS ON TXWY A. GND CTL CONFIRMED ACFT X WAS ON TXWY A AND I RECLRED ACFT Y. OUR TWR IS SO LOW I'M NOT ABLE TO DIFFERENTIATE BTWN ACFT ON THE RWY OR TXWY. THIS IS A CONTINUING PROB AT TYS WITH MOST INCIDENTS NOT BEING RPTED. THE BEST SOLUTION WOULD BE A TALLER TWR. NEXT MAY BE SOME TYPE OF GND DETECTION EQUIP AND/OR VIDEO CAMERA AT STRATEGIC LOCATIONS.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.