Last July SRT Derailment "Track Deformation Expanded Due to Temperature Rise"... Safety Recommendations to SR and Others

The SRT high-speed train derailment accident that occurred last July within the Daejeon Jochajang Station premises on the Gyeongbu High-Speed Line upbound track was found to have been caused by track deformation that expanded as multiple trains passed after buckling (a phenomenon where the rail expands and bulges sharply in the transverse direction) occurred in the joint rail section of the long rail. Although track deformation was detected one hour before the accident, appropriate control or maintenance was not carried out. The Aviation and Railway Accident Investigation Board (ARAIB) issued safety recommendations to Korail, SR, and the Korea Rail Network Authority.

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ARAIB announced the investigation results on the derailment accident of SR's SRT high-speed train No. 338, which occurred around 3:20 p.m. on July 1 last year within the Daejeon Jochajang Station premises on the Gyeongbu High-Speed Line upbound track (located in Daedeok-gu, Daejeon) on the 3rd.

The accident train passed the track deformation site about 5 meters ahead of the N34A turnout on the Gyeongbu High-Speed Line within the Daejeon Jochajang Station premises at a speed of approximately 98 km/h. During this, the front bogie (independent bogie) wheels of the second car in the train's direction of travel (car No. 1) first derailed to the right side of the track due to severe lateral vibration and impact. The train driver applied the emergency brake after feeling severe lateral vibration and impact, but the front bogie wheels of the last 10th car (rear power car) also derailed to the right side of the track. The train finally stopped about 338 meters past the initial derailment point.

As a result of this accident, 11 passengers were injured, and damage occurred to vehicles, rails, sleepers, track circuits, and overhead line equipment. Additionally, 211 trains were affected in operation (14 canceled, 197 delayed). The total estimated damage cost from this accident was 6.9 billion KRW.

ARAIB immediately began investigating the cause of the accident by inspecting the vehicle, debris, and rail conditions, and securing and analyzing operation records, wireless recordings, and CCTV footage. The initial investigation confirmed that track maintenance was insufficient in the accident section (the connection section between high-speed and conventional lines), resulting in track deformation. It was also confirmed that the drivers of the preceding KTX train about one hour before the accident and the preceding SRT train three minutes before the accident detected or sensed the track deformation, but appropriate control or maintenance was not performed.

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ARAIB concluded that the cause of the accident was the expansion of track deformation as multiple trains passed after buckling occurred in the joint rail section of the long rail. The joint rail is a forged rail used to connect different rails in railway tracks, and buckling refers to the phenomenon where the rail expands due to temperature rise, causing axial pressure to exceed lateral resistance, resulting in rapid transverse bulging.

Contributing factors included insufficient track maintenance despite the structural vulnerability of the joint rail and the failure to perform appropriate control or maintenance despite the detection of track deformation about one hour before the accident.

The joint rail section had a higher possibility of ballast settlement and floating sleepers than the general rail section, structural vulnerabilities such as the rail surface being subjected to large forces due to differences in track stiffness, track twisting exceeding maintenance standards causing large lateral pressure on the rail, insufficient ballast leading to weak lateral resistance, and unstable track conditions due to the absence of long rail resetting, as revealed by the investigation.

Furthermore, although track twisting exceeded maintenance standards, appropriate maintenance was not performed; track maintenance was insufficient, including inadequate summer and routine patrol inspections; rail temperature rose above 50°C on the accident day, likely causing axial pressure accumulation in the long rail due to thermal expansion; and despite the preceding KTX train driver detecting track deformation about one hour before the accident, improper reporting systems, inappropriate terminology, unclear inspection location notifications, and insufficient inspections prevented appropriate control or maintenance beforehand.

Accordingly, ARAIB issued a total of nine safety recommendations: five to Korail, one to SR, and three to the Korea Rail Network Authority to prevent recurrence.

This investigation result was finalized through procedures including external expert consultation, hearing opinions from related parties, and committee deliberation and resolution. The full investigation report can be accessed on the ARAIB website from 11 a.m. on the 3rd.

An ARAIB official stated, "We will immediately send the investigation report to related organizations to submit safety recommendation implementation plans or results, and regularly check the implementation status of safety recommendations to do our best to prevent similar accidents from recurring."

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