Narrative:

Aircraft X was departing runway 04. I was working clearance delivery/controller in charge and monitoring LC1 as required. As the aircraft X became airborne; he asked LC1 'tower; did you see that?' the local control-1 asked if aircraft Y who was supposed to be turning at twy 'Q' had entered the runway. At that point I looked at aircraft Y and the aircraft was moving slowly forward as if they were crossing the runway. However; it was night and depth perception can be difficult at night. Aircraft X responded to LC1 by saying yes he did enter the runway and they had to maneuver to the left to avoid aircraft Y. Ground control then told aircraft Y that they were supposed to be turning on 'Q' but they had missed the turn. Aircraft Y replied asking if he should turn right on twy 'north' on the other side of runway 04. Ground control then explained that there was an aircraft departing and aircraft Y replied; 'ok; um; obviously we missed it.' the ground control then continued taxiing aircraft Y towards runway 13R. I immediately notified the TRACON controller in charge as explained on the checklists and I offered a break to both controllers considering the gravity of the situation that had just occurred. Both declined and continued working until relief arrived.I have sadly done this report on runway incursions before. I will once again say this facility needs some sort of safety logic system. The amount of runway incursions we have here is unacceptable and I say again; it is not a matter of if we will have a runway related accident; it is only a matter of when. Sat was slated to get asde-X; but this equipment ended up in a different facility. Nonetheless; had we had that equipment now; this would not had happened because we would have seen and been assured of the position of the aircraft. Additionally; the safety logic alarms would have predicted the offending aircraft passing the 'stop bars' while towards runway 04. I am fully aware of the cost associated with safety logic systems and that based solely on traffic volume and complexity it is not necessary. However; the cost of an accident is far greater.

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Original NASA ASRS Text

Title: SAT Controller and air carrier Captain took evasive action to miss an aircraft that entered the active runway without clearance.

Narrative: Aircraft X was departing runway 04. I was working CD/CIC and monitoring LC1 as required. As the Aircraft X became airborne; he asked LC1 'Tower; did you see that?' The LC-1 asked if Aircraft Y who was supposed to be turning at TWY 'Q' had entered the runway. At that point I looked at Aircraft Y and the aircraft was moving slowly forward as if they were crossing the runway. However; it was night and depth perception can be difficult at night. Aircraft X responded to LC1 by saying yes he did enter the runway and they had to maneuver to the left to avoid Aircraft Y. GC then told Aircraft Y that they were supposed to be turning on 'Q' but they had missed the turn. Aircraft Y replied asking if he should turn right on TWY 'N' on the other side of RWY 04. GC then explained that there was an aircraft departing and Aircraft Y replied; 'Ok; um; obviously we missed it.' The GC then continued taxiing Aircraft Y towards runway 13R. I immediately notified the TRACON CIC as explained on the checklists and I offered a break to both controllers considering the gravity of the situation that had just occurred. Both declined and continued working until relief arrived.I have sadly done this report on runway incursions before. I will once again say this facility needs some sort of safety logic system. The amount of runway incursions we have here is unacceptable and I say again; it is not a matter of if we will have a runway related accident; it is only a matter of when. SAT was slated to get ASDE-X; but this equipment ended up in a different facility. Nonetheless; had we had that equipment now; this would not had happened because we would have seen and been assured of the position of the aircraft. Additionally; the safety logic alarms would have predicted the offending aircraft passing the 'stop bars' while towards RWY 04. I am fully aware of the cost associated with safety logic systems and that based solely on traffic volume and complexity it is not necessary. However; the cost of an accident is far greater.

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.