What is the primary purpose of the EN 15654-1 standard?

The primary purpose of EN 15654-1 is to specify the technical requirements for the physical on-track site where vertical wheel forces of in-service railway vehicles are measured. It standardizes the track geometry and foundation to ensure that measurements are accurate, repeatable, and comparable across different locations and systems.

Why is track geometry so critical for measurement sites under this standard?

Track geometry is critical because any irregularity, such as a bump, dip, or curve, can induce dynamic forces that are not related to the vehicle's condition. A perfectly straight, level, and smooth track, as mandated by the standard, minimizes these external influences, ensuring that the measured forces are a true reflection of the wheel and vehicle performance.

Does EN 15654-1 specify the type of sensors to be used for measurement?

No, EN 15654-1 does not specify the measurement technology or the sensors themselves (e.g., strain gauges, fiber optics). Its scope is strictly limited to defining the characteristics and quality of the track section—the measurement 'site'—to create a standardized environment for whatever sensing technology is deployed.

How do measurements from EN 15654-1 compliant sites improve railway safety?

By ensuring accurate measurements, these sites enable the reliable detection of dangerous conditions like overloaded wagons, imbalanced loads, and high dynamic impacts from wheel defects (like wheel flats). Identifying these issues in real-time allows operators to take immediate action, such as stopping a train or scheduling urgent maintenance, thereby preventing potential derailments and track damage.

Europe Sets New Standard for Rail Force Measurement Sites

EN 15654-1 standardizes on-track sites for accurate vertical wheel force measurement. This ensures reliable data for enhanced railway safety, predictive maintenance, and efficient network operations.

December 15, 2024 2:02 am

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Understanding EN 15654-1: On-Track Measurement Sites for Vertical Wheel Forces

EN 15654-1 is a European Standard that specifies the essential requirements for on-track measurement sites used to determine the vertical forces exerted by the wheels of in-service railway vehicles. This standard is critical for ensuring the accuracy and comparability of data collected from wayside monitoring systems, which are fundamental to modern railway safety and maintenance.

The primary function of this standard is not to define the measurement technology or sensors themselves, but rather to establish a uniform set of conditions for the physical track section where the measurement takes place. By standardizing the measurement site, EN 15654-1 ensures that the collected force data is a true representation of the vehicle’s condition, free from distortions caused by poor track geometry or an unstable foundation.

Key Objectives and Scope of the Standard

The implementation of EN 15654-1 aims to achieve several key objectives that are vital for the interoperability and safety of the European rail network:

Accuracy and Repeatability: To provide a framework that allows for the consistent and accurate measurement of vertical wheel forces, regardless of the specific measurement system being used.
Comparability: To ensure that data from different measurement sites across various networks can be reliably compared, facilitating network-wide vehicle monitoring.
Safety Assurance: To enable the reliable detection of unsafe vehicle conditions, such as wheel overloads, imbalanced loads, and dynamic force impacts from wheel defects (e.g., wheel flats).
Infrastructure Protection: To help manage and mitigate the impact of high vertical forces on track components, including rails, sleepers, and bridges.

The scope of this part of the standard is specifically focused on the characteristics of the track at the measurement location for vehicles in service, covering mainline and freight operations.

Core Technical Requirements for a Compliant Measurement Site

To comply with EN 15654-1, a measurement site must meet stringent criteria across several technical areas. These requirements are designed to create an ideal measurement environment by minimizing external variables that could influence force readings.

Track Geometry and Quality

The geometry of the track section is the most critical aspect. The standard mandates extremely tight tolerances to prevent dynamic forces from being induced by the track itself. Key parameters include:

Longitudinal Level: The track through the measurement zone must be exceptionally smooth and level, without dips or bumps that would cause the vehicle’s suspension to oscillate.
Alignment: The measurement site must be located on a perfectly straight section of track (tangent track). Curves introduce lateral forces and uneven vertical loading, which would corrupt the measurements.
Cant (Superelevation): On a straight track, the cant must be zero. Both rails must be at the exact same height to ensure a balanced vertical force distribution.
Track Gauge: The distance between the rails must be consistent and within very strict limits to ensure stable wheel-rail interaction.
Rail Condition: The rail surface must be free from defects like corrugations, head checks, or significant wear that could create noise in the force data.

Substructure and Foundation

The stability of the track’s foundation is crucial for accurate measurement. The standard requires:

Stable Foundation: The substructure, including ballast, sub-ballast, and formation, must be well-compacted and stable to prevent any deflection under load.
Component Quality: Sleepers (ties) and fastening systems must be in excellent condition, providing consistent and rigid support to the rails. This ensures that the force is transmitted directly to the sensors without being dampened or altered by loose components.

Approach and Departure Zones

The quality of the track is not only important at the point of measurement but also in the sections leading to and from it. EN 15654-1 specifies requirements for approach and departure zones (typically tens of meters long) to ensure the vehicle is dynamically stable before it reaches the sensors. Any track irregularities or curves in these zones could induce vehicle oscillations that persist as it passes over the measurement system.

Classification of Measurement Sites

While the standard provides a common framework, it acknowledges that different applications may require different levels of accuracy. It defines classes of measurement sites based on their geometric quality and the intended use of the data. This allows for a cost-effective approach where less critical monitoring may use a site with slightly wider tolerances.

Site Class	Primary Application	Typical Geometric Tolerance Level	Key Focus
Class 1	High-precision measurements, scientific research, vehicle acceptance testing, and calibration.	Very Strict	Highest possible accuracy and repeatability to isolate vehicle-induced forces.
Class 2	Operational network monitoring, overload detection, and identification of severe wheel defects.	Strict	Reliable and robust detection of safety-critical faults on in-service vehicles.
Class 3	General trend monitoring, statistical data collection for asset management.	Moderate	Cost-effective data collection where absolute precision is less critical than identifying long-term trends.

Importance in the Modern Railway Industry

EN 15654-1 is a cornerstone of data-driven railway operations. Compliant measurement sites provide the reliable data needed for:

Predictive Maintenance: By accurately measuring dynamic forces, systems can detect developing wheel flats, bearing problems, or suspension faults long before they become catastrophic failures.
Enhanced Safety: Real-time detection of overloaded or imbalanced wagons prevents derailments and reduces damage to infrastructure.
Fair Access and Charging: For networks with multiple operators, force data can be used to calculate track access charges based on the actual wear and tear each vehicle imposes on the infrastructure.
Infrastructure Lifecycle Management: Understanding the true load spectrum on tracks and bridges allows infrastructure managers to better predict maintenance needs and extend asset life.

Conclusion

EN 15654-1 provides the foundational rules for establishing reliable on-track wheel force measurement sites. By meticulously defining the required conditions for track geometry, stability, and quality, the standard ensures that the data gathered is accurate, trustworthy, and comparable across the entire rail network. This enables a transition from reactive to proactive maintenance and safety management, making railways a safer and more efficient mode of transport.

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