On October 9, 2024, at 10:38 p.m., five freight wagons forming part of train number 81111 derailed on track line M202 at km 480+990, between stations Mrzlo Polje and Karlovac.
Train number 81111 operated on the route Šoići – Sisak Caprag and consisted of locomotive number 91 80 6193 098-1 and a total of 29 wagon sloaded with diesel fuel and butane. The train was operated by a trainee driver under the supervision of a mentor driver.
Wagon number 33 78 7960 119-9 derailed with the first axle of its second bogie in the direction of travel (rail curve) at km 480+990. At the location of the derailment a speed restriction (vmax 20 km/h) had been introduced by the infrastructure manager from June 30, 2024, by telegram 68F (65F) due to track deformation. The freight train was operating within the prescribed speed restriction. After the derailment of the first axle of the second bogie on wagon number 33 78 7960 119-9 (17th wagon in the train formation), the train continued to move and upon encountering switch number 48 at station Karlovac, at km 477+619, the second axle of the second bogie also derailed in the direction of travel, as did the following four wagons with both bogies in sequence: 33 78 7960 069-6 (18th wagon), 33 78 7960 187-6 (19th wagon), 33 78 7991 042-6 (20th wagon), and wagon 33 78 7960 131-4 (21st wagon) with its first bogie in the direction of travel.
No injuries or fatalities occurred in this serious accident, but major material damage was caused to the railway infrastructure and vehicles.
The causal factor of the derailment was a combination of events related to physical and dynamic effects resulting from multiple consecutive changes in train speed when approaching a deformed section of the track with design superelevation and curve radius, on which a temporary speed restriction was implemented, leading to an unfavorable shift in the center of gravity and wheel unloading of the outer wheel of the tank wagon in the track curve (chapter 3.2.1., 4.3.3.).
Contributing factor:
- none.
System factor:
– previously determined rail breakages or track deformations on the track section Mrzlo Polje–Karlovac (Chapter 4.3.3.),
– continuous alternation of the introduction and cancellation of speed restrictions on the Mrzlo Polje–Karlovac track section over a continuous period from the end of 2023 due to rail breakage or track deformation (chapter 4.3.3.),
– the last overhaul of the Mrzlo Polje-Karlovac track section was in 1996 (chapter 4.1.1.).
The Agency for Investigation of Accidents in Air, Maritime and Railway Transport, based on the conducted investigation of this accident, in order to increase the safety of the railway system, addresses the following safety recommendations to the Agency for Railway Safety:
✓ AIN/06-SR-12/2026
The infrastructure manager should improve the implementation and supporting procedures within its Safety Management System (SMS) regarding the analysis and monitoring of leading indicators (accident precursors, such as the implementation and cancellation of temporary speed restrictions caused by rail breaks or track deformations). In cases where frequent and recurring implementations of temporary speed restrictions are identified on the same section of track, the infrastructure manager should through the development and implementation of binding action plans, as well as the reassessment and revision of risk control measures execute long-term and comprehensive technical-infrastructural solutions instead of short-term temporary remediations, in order to timely prevent the impairment of the dynamic stability of railway vehicles and ensure permanently safe traffic operations.
✓ AIN/06-SR-13/2026
When introducing speed restrictions relative to the speeds prescribed in the working timetables, the infrastructure manager should minimize speed fluctuations in accordance with the track configuration to prevent the sloshing effect of liquid in tank wagons.
✓ AIN/06-SR-14/2026
The infrastructure manager should harmonize and correct the differences in the kilometer positions of the track (km 481+800 to 481+400 and km 477+800 to 477+700) that were observed during the analysis of the speed of train no. 81111.
