Narrative:

At the time of the event I was working local control north. Ground control had an [aircraft] taxiing to the midfield blast fence under escort by a miami ramp vehicle. I gave ground control permission to cross runway 8L and 8R with the ramp vehicle and 767. After they completed crossing runway 8L and 8R without incident from what I recall ground control then instructed the ramp vehicle and B767 to proceed via taxiway Q and hold short of runway 12 at Z. Local control south had a B737 landing short final on runway 12. The local south controller asked ground control if the vehicle was holding short of runway 12. At that time I noticed the ramp vehicle entering runway 12 at intersection Q2 and I immediately shouted to local south to send the B737 around at which time he did. The B737 was in the flare and nearly touched down. It is in my opinion that had the B737 not gone around the aircraft and the ramp vehicle would have collided. The airport surface detection equipment; model X (asde-X) surveillance equipment which was in full logic mode did not alert when the ramp vehicle entered the runway. It is in my opinion that it did not alert because it was in rain mode due to inclement weather in the area and did not recognize an unknown unmarked target as a vehicle. Miami ramp vehicles should be equipped with a transponder that the asde equipment is able to detect regardless of the setting its in.

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Original NASA ASRS Text

Title: A Tower Local Controller observed a vehicle entering a runway with an aircraft on short final. The Tower ASDE-X equipment did not alert the controllers.

Narrative: At the time of the event I was working Local Control North. Ground Control had an [aircraft] taxiing to the Midfield blast fence under escort by a Miami ramp vehicle. I gave ground control permission to cross Runway 8L and 8R with the ramp vehicle and 767. After they completed crossing Runway 8L and 8R without incident from what I recall Ground Control then instructed the ramp vehicle and B767 to proceed via taxiway Q and hold short of Runway 12 at Z. Local Control South had a B737 landing short final on Runway 12. The Local South Controller asked ground control if the vehicle was holding short of runway 12. At that time I noticed the ramp vehicle entering runway 12 at intersection Q2 and I immediately shouted to Local South to send the B737 around at which time he did. The B737 was in the flare and nearly touched down. It is in my opinion that had the B737 not gone around the aircraft and the ramp vehicle would have collided. The Airport Surface Detection Equipment; Model X (ASDE-X) surveillance equipment which was in full logic mode did not alert when the ramp vehicle entered the runway. It is in my opinion that it did not alert because it was in rain mode due to inclement weather in the area and did not recognize an unknown unmarked target as a vehicle. Miami ramp vehicles should be equipped with a transponder that the ASDE equipment is able to detect regardless of the setting its in.

Data retrieved from NASA's ASRS site 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.