Narrative:

Ground control north; requested permission to cross runway 8R at mia. I instructed air carrier X to position and hold runway 8R. I observed to crossing aircraft turn up runway 8R. Ground control alerted me that the aircraft had gotten lost. I observed to aircraft under tow exit runway 8R. I asked ground control north if he was clear. Response; 'he looks clear to me.' I ascertained the aircraft under tow looked clear on the asde. I asked clearance delivery if he looked clear. Answer; 'affirmative.' I departed air carrier X; amass alarmed as air carrier X was rolling past it. Too late to abort his takeoff roll. The asde showed to crossing aircraft clear -- amass determined he wasn't. This is a far too common occurrence at mia. The amass is often wrong due to alignment problems; construction; barriers for closed turnoffs; and misinterped flight paths. Until the problems are resolved; this tool needs to be shelved in determining; without any chance of appeal; whether an error has occurred! If the tower controllers; all the controllers; determine the aircraft is no factor; what good is a tool that alerts; falsely; when no corrective action is possible?

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Original NASA ASRS Text

Title: MIA CTLR EXPERIENCED AMASS ALERT AFTER VISUALLY ENSURING THAT XING TFC WAS CLR AND ELECTED NOT TO ABORT ACFT BECAUSE OF ROLLING SPD.

Narrative: GND CTL N; REQUESTED PERMISSION TO CROSS RWY 8R AT MIA. I INSTRUCTED ACR X TO POS AND HOLD RWY 8R. I OBSERVED TO XING ACFT TURN UP RWY 8R. GND CTL ALERTED ME THAT THE ACFT HAD GOTTEN LOST. I OBSERVED TO ACFT UNDER TOW EXIT RWY 8R. I ASKED GND CTL N IF HE WAS CLR. RESPONSE; 'HE LOOKS CLR TO ME.' I ASCERTAINED THE ACFT UNDER TOW LOOKED CLR ON THE ASDE. I ASKED CLRNC DELIVERY IF HE LOOKED CLR. ANSWER; 'AFFIRMATIVE.' I DEPARTED ACR X; AMASS ALARMED AS ACR X WAS ROLLING PAST IT. TOO LATE TO ABORT HIS TKOF ROLL. THE ASDE SHOWED TO XING ACFT CLR -- AMASS DETERMINED HE WASN'T. THIS IS A FAR TOO COMMON OCCURRENCE AT MIA. THE AMASS IS OFTEN WRONG DUE TO ALIGNMENT PROBS; CONSTRUCTION; BARRIERS FOR CLOSED TURNOFFS; AND MISINTERPED FLT PATHS. UNTIL THE PROBS ARE RESOLVED; THIS TOOL NEEDS TO BE SHELVED IN DETERMINING; WITHOUT ANY CHANCE OF APPEAL; WHETHER AN ERROR HAS OCCURRED! IF THE TWR CTLRS; ALL THE CTLRS; DETERMINE THE ACFT IS NO FACTOR; WHAT GOOD IS A TOOL THAT ALERTS; FALSELY; WHEN NO CORRECTIVE ACTION IS POSSIBLE?

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.