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?