Narrative:

I was training on ground control/flight data. The developmental issued a taxi route to aircraft X that included an inactive runway crossing and a runway hold short instruction of the active runway. Aircraft X read back the clearance correctly. The developmental was falling behind with a high volume of work and frequency congestion from multiple simultaneous calls. To my right; the local 1 position had just finished a position relief briefing and another developmental was plugged in receiving a briefing from the local 1 OJT (on job training) instructor. The controller-in-charge position was also conducting a position relief briefing to my left. Behind me was the local 2 controller and other controllers who had just been relieved; exiting the tower cab; and an intern who was plugged in monitoring. The tower cab was crowded with controllers all standing shoulder to shoulder and little ability to move.I recognized my developmental was falling too far behind and began to prepare to take over the frequency. My developmental standing was initially blocking my view of the taxiways intersection. Once I could re-position myself to gain a view of aircraft X I observed aircraft X on the active runway at an intersection of another runway. My developmental was looking at another aircraft calling from a ramp and transmitting to them when I keyed over him to tell aircraft X to exit the runway at the closest and quickest way off the active runway. Aircraft X had crossed approximately 750-1000 feet in front of another aircraft on the same runway at taxi speed.multiple factors led to this runway incursion unfolding beginning with the reason why aircraft X requested taxi. Aircraft X is part of a [company] located [on the east side of the airport]. This [company's] fuel tank is located on the northwest corner of the airport which requires two runway crossings each way to get from their ramp to their fuel tank in order to refuel aircraft. It is quite common to have these aircraft request taxi from their ramp to refuel; and then back to the ramp to park during peak hours of traffic volume. We have worked around the needs of the [company]. Educating the [company] of the hazards this operation presents; especially during peak hours; and familiarization with the airport layout.a crowded tower cab with a lot of activity changing simultaneously combined with multiple obstructions to view to all controllers; including myself and the local 1 controller; was also a contributing factor. Better pre-planning of position relief briefings and limiting of the number of people in the cab to aid in mobility and visibility.the taxiway intersection where the incursion occurred is a known hotspot due to taxiway complexity which also may have played a part in the pilot's interpretation of the instruction. Aircraft X had encroached upon the runways intersection when I instructed them to exit; it was too late to stop aircraft X short.

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Original NASA ASRS Text

Title: Two air traffic controllers reported on a runway incursion that took place while conducting on-the-job training. The aircraft was issued taxi instructions to hold short of an active runway. The student pilot read back the instructions correctly yet taxied on to the active runway as another aircraft was landing. A shift change was occurring in the Tower and was crowded with people obscuring the controllers' views of the airport.

Narrative: I was training on Ground Control/Flight Data. The developmental issued a taxi route to Aircraft X that included an inactive runway crossing and a runway hold short instruction of the active runway. Aircraft X read back the clearance correctly. The developmental was falling behind with a high volume of work and frequency congestion from multiple simultaneous calls. To my right; the Local 1 position had just finished a position relief briefing and another Developmental was plugged in receiving a briefing from the Local 1 OJT (On Job Training) Instructor. The Controller-in-Charge position was also conducting a position relief briefing to my left. Behind me was the Local 2 controller and other controllers who had just been relieved; exiting the tower cab; and an intern who was plugged in monitoring. The tower cab was crowded with controllers all standing shoulder to shoulder and little ability to move.I recognized my Developmental was falling too far behind and began to prepare to take over the frequency. My developmental standing was initially blocking my view of the taxiways intersection. Once I could re-position myself to gain a view of Aircraft X I observed Aircraft X on the active Runway at an intersection of another runway. My developmental was looking at another aircraft calling from a ramp and transmitting to them when I keyed over him to tell Aircraft X to exit the runway at the closest and quickest way off the active runway. Aircraft X had crossed approximately 750-1000 feet in front of another aircraft on the same runway at taxi speed.Multiple factors led to this runway incursion unfolding beginning with the reason why Aircraft X requested taxi. Aircraft X is part of a [company] located [on the East side of the airport]. This [company's] fuel tank is located on the Northwest corner of the airport which requires two runway crossings each way to get from their ramp to their fuel tank in order to refuel aircraft. It is quite common to have these aircraft request taxi from their ramp to refuel; and then back to the ramp to park during peak hours of traffic volume. We have worked around the needs of the [company]. Educating the [company] of the hazards this operation presents; especially during peak hours; and familiarization with the airport layout.A crowded Tower cab with a lot of activity changing simultaneously combined with multiple obstructions to view to all controllers; including myself and the Local 1 Controller; was also a contributing factor. Better pre-planning of position relief briefings and limiting of the number of people in the cab to aid in mobility and visibility.The taxiway intersection where the incursion occurred is a known hotspot due to taxiway complexity which also may have played a part in the pilot's interpretation of the instruction. Aircraft X had encroached upon the runways intersection when I instructed them to exit; it was too late to stop Aircraft X short.

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.