Derailment
Overview
Derailment (Korean: 탈선; Hanja: 脫線) is an accident in which the wheels of a railway vehicle leave the track (rails) and depart from the designated running path. In a narrow sense, it refers to the physical accident of a train leaving the track, but figuratively it can also refer to the act of a person or organization departing from established norms, common sense, or duty. Railway derailments can lead to mass casualties, making them a top-priority monitoring target in railway safety management.
Main Content
Definition and Physical Principles
Railway vehicles maintain their course as the protruding rim called the flange on the wheel follows the inside of the rail. If the balance among lateral force (sideways force) generated at the contact point between wheel and rail, wheel load (vertical load with which the wheel presses the rail), and friction is broken, the wheel climbs onto or leaves the rail. This is evaluated by the 'derailment coefficient'; generally, when the lateral force/wheel load ratio exceeds about 0.8, the risk of derailment increases sharply.
Major Causes
1. Track defects: rail breakage, track distortion, turnout (point) failure, sleeper corrosion, etc.
2. Vehicle defects: damage to wheels/bogies, braking system abnormalities, unbalanced loading of the car body
3. Operating factors: speeding, sudden braking, ignoring signals, exceeding speed on curves
4. Natural factors: earthquakes, inflow of soil and sand due to heavy rain, landslides, rail deformation (buckling) caused by extreme temperatures
5. External factors: obstacles on the track, vehicle collisions, deliberate terrorism/sabotage
Types
- Full derailment: a major accident in which multiple vehicles leave the track in a chain reaction
- Partial derailment: a case in which only some wheels leave the track and soon return
- Turnout derailment: a typical accident occurring at a track switch
- High-speed derailment: when it occurs on high-speed rail, the scale of damage is maximized
Damage and Ripple Effects
Derailments can lead to vehicle overturning, collisions, fires, and leakage of hazardous materials. The 2013 Santiago de Compostela derailment in Spain (79 deaths) and the 2005 JR Fukuchiyama Line derailment in Japan (107 deaths) are representative catastrophes. In Korea, the 2018 Gangneung Line KTX derailment (14 injuries) is representative. Derailments cause not only casualties but also enormous recovery costs and service suspension due to damage to tracks and vehicles.
Prevention and Countermeasures
- Regular track inspection and operation of track geometry cars
- Real-time monitoring of wheel and bogie conditions
- Introduction of derailment prevention guards (guard rails) and automatic train protection systems (ATP/ETCS)
- Deceleration on curves and compliance with speed limits
- Preemptive service control in preparation for extreme weather
Latest Trends
In 2024–2025, AI-based predictive maintenance and digital twin technology are being actively introduced to prevent derailments. This approach uses machine learning to analyze vibration, noise, and load data collected through sensors and IoT to detect abnormal signs in advance. In addition, as heat waves and localized heavy rains caused by climate change increase the risk of rail buckling and roadbed loss, extreme-weather-responsive track management has emerged as a major task. In Korea as well, Korea National Railway and Korail are expanding the application of autonomous driving and unmanned inspection technology, and a project to convert to an ETCS Level 2 train control system is underway. Meanwhile, in its figurative sense, 'derailment' is still widely used in political and media ethics debates to refer to deviation from norms.
Related Topics
- [[Rail transport]]
- [[Train]]
- [[Traffic accident]]
- [[High-speed rail]]
- [[Railway safety]]