Tower issued a go around for a B757 due to vehicles past the runway hold short line.

Attributes
ACN	576178
Time
Date	200302
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : dfw.airport
State Reference	TX
Altitude	agl single value : 30
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : dfw.tower
Operator	common carrier : air carrier
Make Model Name	B757 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	descent : approach
Route In Use	approach : visual
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : multi engine pilot : flight engineer
Experience	flight time last 90 days : 130 flight time total : 5000 flight time type : 1200
ASRS Report	576178
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	ground encounters : vehicle other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : amass other controllerb
Resolutory Action	controller : issued new clearance controller : issued advisory flight crew : took precautionary avoidance action flight crew : took evasive action flight crew : executed go around
Supplementary
Problem Areas	ATC Human Performance Airport Flight Crew Human Performance
Primary Problem	ATC Human Performance

Narrative:

While on final visual approach to runway 35C at dfw, we noticed 2 trucks approaching runway 35C on taxiway M6. The 2 vehicles appeared to be airport vehicles. They approached the runway, but did not cross over the runway edge markings. At about 30 ft AGL and starting to flare, tower directed us to go around. We performed a rejected landing and flew a tower directed runway heading to 3000 ft. As we flew past the vehicles while going around, we saw that the trucks were between the painted runway safety line (hold short line) and the painted runway edge. Tower explained that he had an amass alert and that is why he directed us to go around. We were subsequently vectored back for an uneventful visual approach and landing. Apparently dfw was performing calibration checks because of several false alerts. Why they were performing checks while aircraft are on close final, I do not know. I do know that this alert was not a false one.

Original NASA ASRS Text

Title: TWR ISSUED A GAR FOR A B757 DUE TO VEHICLES PAST THE RWY HOLD SHORT LINE.

Narrative: WHILE ON FINAL VISUAL APCH TO RWY 35C AT DFW, WE NOTICED 2 TRUCKS APCHING RWY 35C ON TXWY M6. THE 2 VEHICLES APPEARED TO BE ARPT VEHICLES. THEY APCHED THE RWY, BUT DID NOT CROSS OVER THE RWY EDGE MARKINGS. AT ABOUT 30 FT AGL AND STARTING TO FLARE, TWR DIRECTED US TO GO AROUND. WE PERFORMED A REJECTED LNDG AND FLEW A TWR DIRECTED RWY HEADING TO 3000 FT. AS WE FLEW PAST THE VEHICLES WHILE GOING AROUND, WE SAW THAT THE TRUCKS WERE BTWN THE PAINTED RWY SAFETY LINE (HOLD SHORT LINE) AND THE PAINTED RWY EDGE. TWR EXPLAINED THAT HE HAD AN AMASS ALERT AND THAT IS WHY HE DIRECTED US TO GO AROUND. WE WERE SUBSEQUENTLY VECTORED BACK FOR AN UNEVENTFUL VISUAL APCH AND LNDG. APPARENTLY DFW WAS PERFORMING CALIBRATION CHKS BECAUSE OF SEVERAL FALSE ALERTS. WHY THEY WERE PERFORMING CHKS WHILE ACFT ARE ON CLOSE FINAL, I DO NOT KNOW. I DO KNOW THAT THIS ALERT WAS NOT A FALSE ONE.

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.