Axle load limits and lightweight materials in the European Railway Sector

Regulatory framework and operational challenges

The European railway sector is strictly regulated by precise axle load limits. According to the Commission Implementing Regulation (EU) 2023/1694, which updates the TSI Infrastructure regulation, the technical parameter of “axle load” is defined as the sum of the static vertical forces acting on an axle, divided by gravitational acceleration. (European Union Agency for Railways)

These limits are essential to:

protect the integrity of tracks and infrastructure,
ensure operational safety,
reduce harmful dynamic effects such as vibrations, wear, and deformations.

A recent study (Dynamical Effects of the Increase of the Axle Load on European Freight Railway Vehicles, 2023) estimated that, with well-maintained infrastructure, limits could be raised up to ~30–32.5 tons per axle, provided speed is reduced (80–120 km/h) and suspensions are optimized. (MDPI).

In other words: to increase the load, trains must slow down, bringing with it operational consequences. That is why lightweighting of components becomes a key strategy to preserve performance and competitiveness while remaining within regulatory constraints.

Lightweight materials as an alternative to metals

While metallic alloys (steel, special steels, light alloys) remain the benchmark for strength and certification, they present intrinsic limitations:

relatively high density, resulting in greater unsprung mass, which worsens ride comfort and infrastructure lifespan,
energy and mechanical costs proportional to mass, especially in repeated operations,
design limitations: complex geometries or thin sections are difficult to achieve with conventional technologies.

High-performance polymers and composites: technical advantages for Rail lightweighting

High-performance polymers and advanced composites are reshaping railway engineering. Compared to traditional metals, they offer a significantly lower density, enabling weight reductions of over 40% with the same design.

But lightweighting is not the only advantage:

high mechanical strength and dimensional stability,
durability even in humid environments and under demanding operating conditions,
tolerance to temperature variations and dynamic stresses,
the ability to design complex components with optimized geometries thanks to additive manufacturing.

This translates into design efficiency, fewer assemblies, and reduced maintenance costs. Moreover, unlike traditional supply chains (which may take 2 to 6 months, especially with casting processes), additive manufacturing drastically shortens lead times, ensuring rapid spare parts availability.

Case study: a real application in the Rail sector

A major European operator adopted Roboze additive manufacturing to produce a critical component for special railway systems. Manufactured in Carbon PEEK, the part achieved a weight reduction of over 40% compared to its metallic version, while maintaining mechanical strength and dimensional stability under harsh operating conditions.

Although related to a single component, this result demonstrates the potential of Roboze solutions: when multiple train parts are produced in superpolymers and composites, the overall weight reduction becomes decisive in meeting axle load limits, improving efficiency, and lowering maintenance costs.

Lightweight Rail components for a competitive future

Axle load reduction is no longer just a regulatory challenge but a strategic lever for decision makers and executives in the rail sector. It enables energy efficiency, sustainability, operational continuity and lifecycle cost reduction.

Additive manufacturing with superpolymers and composites makes it possible to rethink railway components as lighter, higher-performing, and on-demand available. An approach that anticipates future industry needs and paves the way for a new standard in European railway transport and lightweight rail components.

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