Wheel flats on freight railcars represent a significant concern for the rail industry due to the damage they can inflict on both rolling stock and track infrastructure. A wheel flat develops when a section of a wheel’s tread becomes flattened, often caused by wheel slide during braking. This defect results in high impact forces each time the flat contacts the rail, accelerating wear and increasing the risk of derailment.
Regulatory Standards
To mitigate such risks, regulatory bodies have implemented strict guidelines. In the U.S., the Code of Federal Regulations (49 CFR § 229.75) defines a defective wheel as one with a flat spot of 2.5 inches (63.5 mm) or more, or two adjoining flat spots of 2 inches (50.8 mm) or more. Railcars with such defects are prohibited from operation.
While the European Union Agency for Railways (ERA) and the International Union of Railways (UIC) do not specify exact flat size limits, they provide comprehensive guidelines for wheel maintenance and manufacturing to prevent such defects.
Industry Lessons from Recent Years
• August 2020 – Llangennech, Wales: A train carrying diesel fuel derailed, causing a major fire and environmental spill. A 230 mm (9-inch) wheel flat developed after a brake system failure, leading to track distortion and derailment. Estimated damages: $75 million.
• October 2022 – Petteril Bridge Junction, UK: A severe wheel flat on a cement railcar led to the derailment of five bogie railcars. The flat developed due to poor adhesion conditions, causing the wheel to stop rotating.
• February 2023 – Gothenburg, Nebraska, USA: A Union Pacific coal train derailed due to high-impact wheels, with a Wheel Impact Load Detector (WILD) reading of 130.6 KIPs—far exceeding the 90 KIP threshold commonly used. Such impacts, often resulting from flats, can severely damage infrastructure.
Detection and Monitoring Limitations
As freight traffic increases across major networks, the risks associated with undetected wheel defects such as wheel flats continue to rise. Traditional detection systems, such as trackside impact detectors and bogie-mounted sensors, are limited in scope and functionality. Trackside detectors are fixed in specific locations and can only measure impact as a railcar passes a particular point – providing snapshots rather than continuous insights. They are incapable of alerting train crews in real time, thus limiting their value for immediate safety interventions. Bogie-mounted sensors, while more proximate to the source of vibration, are costly to implement across an entire fleet and require significant upkeep. These legacy systems also struggle with accurately distinguishing between true faults and benign vibrations, which can lead to delayed or unnecessary maintenance.
Trilogical’s Vibration-Based Health Monitoring Algorithm
Trilogical’s proprietary AI-driven solution marks a breakthrough in railcar health diagnostics. Leveraging advanced vibration analysis, it detects wheel flats in real time using a sensor mounted on the railcar body. This innovative approach helps prevent costly damage related to wheel defects and significantly reduces unplanned downtime.
Recent field tests demonstrated the system’s ability to detect 85% of wheel flats under 2 inches with zero false positives – an unmatched performance compared to existing technologies. By offering continuous, real-time insights throughout the journey, Trilogical’s end-to-end monitoring platform sets a new standard for predictive maintenance and operational safety in freight rail.
Results and Operational Impact
• 85% of vibration data samples from faulty railcars exhibited abnormal peaks.
• In contrast, 100% of samples from healthy railcars showed no such anomalies.
This level of accuracy enables rail operators to:
• Automatically receive alerts for early-stage wheel or structural defects
• Prioritize maintenance scheduling and resource allocation
• Reduce unplanned downtime and improve safety
Trilogical’s AI-powered vibration monitoring platform enhances railcar reliability and safety while reducing maintenance costs. Its scalable, car-mounted design eliminates the need for costly trackside or bogie-specific systems, offering a smarter, real-time approach to freight railcar diagnostics.
