Narrative:

Working local control #2, I had responsibility for runway 28R. A large amount of construction was on-going at the airport. Some of the adjoining txwys to runway 28R were undergoing reconstruction. Traffic landing runway 28R had to either turn off at B3 or expedite to B7. At approximately XA35Z air carrier X landed on runway 28R and T taxied air carrier Y into position with additional traffic, air carrier Z on approximately a 4 mi final. Approximately 40 seconds later, it appeared that air carrier X had slowed and could easily exit the runway at taxiway B5, a reverse taxiway. My view of the runway from taxiway B5 to about B7 was blocked by a tower support column and I had to move to ensure that taxiway B5 was clear. However, I issued exit instructions to air carrier X to 'turn left, then turn right on taxiway B and contact ground.' the pilot repeated the instructions. I did not include a taxiway identifier, because I am certain that air carrier X had already started the left turn off the runway at taxiway B5. Seeing that air carrier X was clearing, I directed my attention to air carrier Y with traffic now approaching a 3 mi final. I had anticipated that air carrier X would be well clear of runway 28R and onto taxiway B, before air carrier Y could start takeoff roll. I issued air carrier Y the traffic on final and issued takeoff clearance. At this point air carrier X was visually behind the tower column. I believed air carrier X off the runway on taxiway B5/B. I then issued landing clearance to air carrier Z, who was on about a 3 mi final. I then coordinated local control #1. As I scanned runway 28R, I saw air carrier X now left of the tower support column, not on taxiway B as had I expected, but on runway 28R approximately 8000 ft down the runway. I started to cancel air carrier Y's takeoff clearance, but air carrier Y was already about 2500 ft down the runway. I don't know if air carrier Y saw the D328, but at this point air carrier X was exiting runway 28R at taxiway B8. In my judgement the safest thing to do was to allow traffic to continue. Neither pilot commented on the operation. I informed the supervisor and was removed from the position. Traffic spacing on final was tight but normal and adequate. Staffing and supervision were fine. I am not sure why I felt so certain that air carrier X was clear. It is possible that I saw what I wanted or expected to see. In any event, I know the runway belonged to air carrier X until completely clear. It is my responsibility to ensure that the runway is clear by visually scanning and direct observation. Since I had planned on using the control instruction for separation, I should have included the taxiway identifier.

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Original NASA ASRS Text

Title: ATCT LCL CTLR CLRS A BA31 FOR TKOF WITHOUT ENSURING D328 IS CLR OF RWY. OTHER ACR TFC ON SHORT FINAL. ARPT TXWYS UNDER CONSTRUCTION, CLOUDING CTLR EXPECTATION WHEN LNDG TFC WOULD CLR RWY.

Narrative: WORKING LCL CTL #2, I HAD RESPONSIBILITY FOR RWY 28R. A LARGE AMOUNT OF CONSTRUCTION WAS ON-GOING AT THE ARPT. SOME OF THE ADJOINING TXWYS TO RWY 28R WERE UNDERGOING RECONSTRUCTION. TFC LNDG RWY 28R HAD TO EITHER TURN OFF AT B3 OR EXPEDITE TO B7. AT APPROX XA35Z ACR X LANDED ON RWY 28R AND T TAXIED ACR Y INTO POS WITH ADDITIONAL TFC, ACR Z ON APPROX A 4 MI FINAL. APPROX 40 SECONDS LATER, IT APPEARED THAT ACR X HAD SLOWED AND COULD EASILY EXIT THE RWY AT TXWY B5, A REVERSE TXWY. MY VIEW OF THE RWY FROM TXWY B5 TO ABOUT B7 WAS BLOCKED BY A TWR SUPPORT COLUMN AND I HAD TO MOVE TO ENSURE THAT TXWY B5 WAS CLR. HOWEVER, I ISSUED EXIT INSTRUCTIONS TO ACR X TO 'TURN L, THEN TURN R ON TXWY B AND CONTACT GND.' THE PLT REPEATED THE INSTRUCTIONS. I DID NOT INCLUDE A TXWY IDENTIFIER, BECAUSE I AM CERTAIN THAT ACR X HAD ALREADY STARTED THE L TURN OFF THE RWY AT TXWY B5. SEEING THAT ACR X WAS CLRING, I DIRECTED MY ATTN TO ACR Y WITH TFC NOW APCHING A 3 MI FINAL. I HAD ANTICIPATED THAT ACR X WOULD BE WELL CLR OF RWY 28R AND ONTO TXWY B, BEFORE ACR Y COULD START TKOF ROLL. I ISSUED ACR Y THE TFC ON FINAL AND ISSUED TKOF CLRNC. AT THIS POINT ACR X WAS VISUALLY BEHIND THE TWR COLUMN. I BELIEVED ACR X OFF THE RWY ON TXWY B5/B. I THEN ISSUED LNDG CLRNC TO ACR Z, WHO WAS ON ABOUT A 3 MI FINAL. I THEN COORDINATED LCL CTL #1. AS I SCANNED RWY 28R, I SAW ACR X NOW L OF THE TWR SUPPORT COLUMN, NOT ON TXWY B AS HAD I EXPECTED, BUT ON RWY 28R APPROX 8000 FT DOWN THE RWY. I STARTED TO CANCEL ACR Y'S TKOF CLRNC, BUT ACR Y WAS ALREADY ABOUT 2500 FT DOWN THE RWY. I DON'T KNOW IF ACR Y SAW THE D328, BUT AT THIS POINT ACR X WAS EXITING RWY 28R AT TXWY B8. IN MY JUDGEMENT THE SAFEST THING TO DO WAS TO ALLOW TFC TO CONTINUE. NEITHER PLT COMMENTED ON THE OP. I INFORMED THE SUPVR AND WAS REMOVED FROM THE POS. TFC SPACING ON FINAL WAS TIGHT BUT NORMAL AND ADEQUATE. STAFFING AND SUPERVISION WERE FINE. I AM NOT SURE WHY I FELT SO CERTAIN THAT ACR X WAS CLR. IT IS POSSIBLE THAT I SAW WHAT I WANTED OR EXPECTED TO SEE. IN ANY EVENT, I KNOW THE RWY BELONGED TO ACR X UNTIL COMPLETELY CLR. IT IS MY RESPONSIBILITY TO ENSURE THAT THE RWY IS CLR BY VISUALLY SCANNING AND DIRECT OBSERVATION. SINCE I HAD PLANNED ON USING THE CTL INSTRUCTION FOR SEPARATION, I SHOULD HAVE INCLUDED THE TXWY IDENTIFIER.

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.