Narrative:

We had issued a fire drill for the crash fire rescue equipment team. The false incident was supposed to have occurred on a taxiway. When the fire trucks called me they asked to proceed via the runway. I misunderstood them, thinking they had said via the taxiway. I told them to proceed a requested, but to remain clear of the runway. They did not read back the remain clear instruction and I did not catch it. They then drove out onto the active runway as a C172 (aircraft X) was beginning its takeoff roll. The local controller canceled the takeoff clearance and I told the trucks to exit the runway. The truck exited, and the airplane came to a stop without incident. This problem would have been avoided if I had caught the fact that they did not read back the remain clear instructions.

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Original NASA ASRS Text

Title: JNU GND CTLR MISINTERPS CFR CREW READBACK, ALLOWING CFR TO DRIVE ON THE RWY WITHOUT LCL CTL APPROVAL, LEADING TO A TKOF REJECT.

Narrative: WE HAD ISSUED A FIRE DRILL FOR THE CFR TEAM. THE FALSE INCIDENT WAS SUPPOSED TO HAVE OCCURRED ON A TXWY. WHEN THE FIRE TRUCKS CALLED ME THEY ASKED TO PROCEED VIA THE RWY. I MISUNDERSTOOD THEM, THINKING THEY HAD SAID VIA THE TXWY. I TOLD THEM TO PROCEED A REQUESTED, BUT TO REMAIN CLR OF THE RWY. THEY DID NOT READ BACK THE REMAIN CLR INSTRUCTION AND I DID NOT CATCH IT. THEY THEN DROVE OUT ONTO THE ACTIVE RWY AS A C172 (ACFT X) WAS BEGINNING ITS TKOF ROLL. THE LCL CTLR CANCELED THE TKOF CLRNC AND I TOLD THE TRUCKS TO EXIT THE RWY. THE TRUCK EXITED, AND THE AIRPLANE CAME TO A STOP WITHOUT INCIDENT. THIS PROB WOULD HAVE BEEN AVOIDED IF I HAD CAUGHT THE FACT THAT THEY DID NOT READ BACK THE REMAIN CLR INSTRUCTIONS.

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.