Incident Overview
On 3 June 2022 at approximately 2234 local time, a utility vehicle (UV) operated by the Airport Rescue and Fire Fighting Service (ARFF) departed Fire Station 2 (FS2) on the western side of Changi Airport, carrying the driver and one passenger. The intended destination was Fire Station 3 (FS3) on the eastern side. The driver planned to use a recently opened route that had become available in February 2022 following construction. This route involved traveling via the west perimeter road, north perimeter road, perimeter fence road, then Taxiway Y2, and finally Taxiway MY to reach FS3.
Sequence of Events
Upon arriving at Taxiway Y2 from the perimeter fence road, the UV driver contacted the Runway Controller (RWC) at Changi East Tower via walkie-talkie to request permission to enter Taxiway Y2 and then Taxiway MY, and to travel to a holding position (identified as holding position A) on Taxiway MY. Permission was granted. The driver turned right onto Taxiway Y2 but did not turn left onto Taxiway MY; instead, he continued straight on Taxiway Y2 toward Taxiway MY1, which leads to Runway 3. The driver had mistaken the red stop bar lights at the runway holding position on Taxiway MY1 for those at holding position A on Taxiway MY. The taxiway edge lights on Taxiway MY were not illuminated as no aircraft were expected that night. The driver was checking his handphone for communication procedures and did not observe the signs and markings indicating Runway 3 ahead.
While approaching the lit red stop bar lights on Taxiway MY1, the driver informed the RWC that he was near holding position A. Without verifying the UV's location, the RWC turned off the stop bar lights on Taxiway MY1 and notified the driver. The driver then proceeded forward, unaware that he was entering Runway 3. The RWC then directed her attention to an aircraft on Taxiway A1 and issued a take-off clearance.
After crossing the stop bar lights, the driver stopped the UV on Taxiway MY1 (still believing he was on Taxiway MY) and contacted another controller (Controller B) to request permission to continue to FS3. Controller B granted permission. Meanwhile, the flight crew of an aircraft preparing for take-off observed the UV on the runway and alerted the RWC. The RWC attempted to contact the UV driver but the transmission was garbled and not received. The RWC did not follow up. The UV driver eventually realized he was on the runway, made a U-turn, and returned to Taxiway MY1, then proceeded to FS3 via Taxiway MY.
Investigation Findings
The Transport Safety Investigation Bureau (TSIB) classified the occurrence as an incident. The investigation found that the UV driver had not previously used this route and was unfamiliar with the area. He relied on verbal instructions from colleagues and was distracted by his handphone while driving. The RWC's actions were based on an incorrect assumption about the UV's position; she turned off the stop bar lights on Taxiway MY1 without confirming the vehicle's location. The Advanced Surface Movement Guidance and Control System (A-SMGCS) generated a visual alert indicating a runway incursion after the UV crossed the stop bar lights, but the RWC did not respond to the alert before the incursion was resolved. The presence of the UV was detected by a microwave barrier detector (MBD), which caused the stop bar lights to automatically re-illuminate after the UV crossed.
Safety Actions
Since the incident, a detection system has been installed to allow Controller B to verify if a vehicle requesting permission to transit Taxiway MY is at holding position A. The TSIB issued safety recommendations to enhance procedures and prevent recurrence.