Date: 201902
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Aircraft: B767-300 and 300 ER
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Taxi
ATC / advisory: Tower ZZZ
Second aircraft: A321
Reporter organization: Government
Reporter function: Local; Instructor
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Confusion; Communication Breakdown; Training / Qualification; Situational Awareness; Distraction
Second reporter function: Local
Anomaly: ATC Issue All Types; Conflict Ground Conflict; Less Severe; Deviation / Discrepancy - Procedural Clearance; Ground Incursion Runway
Detector: Person Air Traffic Control
When detected: In-flight; Taxi
Result: Air Traffic Control Issued Advisory / Alert; Air Traffic Control Separated Traffic; Air Traffic Control Issued New Clearance; Flight Crew Executed Go Around / Missed Approach; General Flight Cancelled / Delayed
Contributing factors: Procedure; Aircraft; Human Factors
Primary problem: Procedure

Narrative: Crash and Rescue was called for a Cat 2 for the emergency Aircraft X because of a flap issue; and deployed multiple vehicles in places around Runway 30L. Aircraft X landed without incident; turned off and cleared the runway downfield at taxiway M. The next arrival to Runway 30L was 7 miles away; so Aircraft Y was put into position on Runway 30L awaiting Aircraft X clearing downfield. After Aircraft X cleared the runway; he asked if Crash Rescue could inspect the aircraft outside; and vehicles that were close to Aircraft X approached the aircraft. There were some additional Crash vehicles on the opposite side of the runway that; after Aircraft X cleared the runway and had asked for the inspection; started to position themselves to cross close to Aircraft X at taxiway M.The Crash vehicles asked for a crossing at taxiway M to join the inspection of other vehicles on the other side; and priority was given for them to cross with Aircraft Y still holding in position. The multiple vehicles crossed at taxiway M; however; it was not clear if all vehicles were clear of the runway when the aircraft on final; Aircraft Z; was at a 2 mile final. The decision was made to exit Aircraft Y because of not getting an 'All clear' from the rescue vehicles and not visually able to tell if they were all off the runway. Aircraft Y tried to exit at A2; but was slow getting off; while at the same time Crash vehicles called clear at taxiway M. Aircraft Y appeared to be clear at A2; but the ASDE (Airport Surface Detection Equipment) alerted; and Aircraft Z was sent around.The multiple vehicle crossing at M; delayed calling clear; and aircraft slow to exit all contributed to Aircraft Z going around. While there was a go around; safety was not compromised; and priority was given correctly to the emergency aircraft and vehicles. The timing of all parties involved was just a little slow; but does not demonstrate a pattern or need for any changes.


Second narrative: [Report narrative contained no additional information.]


Synopsis: Tower Controllers reported sending an aircraft around due to Airport Surface Detection Equipment alert for an aircraft exiting the runway.