Narrative:

Working local control; air carrier X was just touching down approximately 1000 ft from approach end of runway. I received an amass alert to 'send aircraft around runway occupied.' the B190 was already slowing down to turn off at the next high speed taxiway. Review of incident showed a vehicle at the approach end of the taxiway; but headed toward the runway at the time air carrier X was crossing the runway threshold. The vehicle turned and never crossed the safety hold short line; however; the asde/amass projected that it was going to. My problem with all this was by the time the system processed the data and issued the alert; it was too late to do anything but scare the hell out of everyone in the tower needlessly.

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Original NASA ASRS Text

Title: MCI LCL CTLR FAILED TO ISSUE MANDATORY AMASS GAR BECAUSE LNDG ACFT WAS ABOUT TO TURN OFF RWY.

Narrative: WORKING LCL CTL; ACR X WAS JUST TOUCHING DOWN APPROX 1000 FT FROM APCH END OF RWY. I RECEIVED AN AMASS ALERT TO 'SEND ACFT AROUND RWY OCCUPIED.' THE B190 WAS ALREADY SLOWING DOWN TO TURN OFF AT THE NEXT HIGH SPD TXWY. REVIEW OF INCIDENT SHOWED A VEHICLE AT THE APCH END OF THE TXWY; BUT HEADED TOWARD THE RWY AT THE TIME ACR X WAS XING THE RWY THRESHOLD. THE VEHICLE TURNED AND NEVER CROSSED THE SAFETY HOLD SHORT LINE; HOWEVER; THE ASDE/AMASS PROJECTED THAT IT WAS GOING TO. MY PROB WITH ALL THIS WAS BY THE TIME THE SYS PROCESSED THE DATA AND ISSUED THE ALERT; IT WAS TOO LATE TO DO ANYTHING BUT SCARE THE HELL OUT OF EVERYONE IN THE TWR NEEDLESSLY.

Data retrieved from NASA's ASRS site as of January 2009 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.