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Every axle counts

Our trusted axle counter system delivers multiple benefits – including some that might surprise you.

Have you ever looked out of a train window and wondered what all those bright yellow “mushrooms” beside the track were? They seem to pop up everywhere – from high-speed lines to metros.

The answer is… they are axle counters. Or more precisely, they are one part of the axle counter system. The full system consists of wheel sensors (attached to both sides of the rail), outdoor electronic units (the mushrooms) and axle counter evaluators which are housed either in secured buildings or inside a trackside cabinet.

Why are axle counter systems so important?

Axle counter systems are one of the cornerstones of railway safety. Information from axle counters is used by the interlocking – the digital “brain” of the railway – to establish train locations as they travel around the network, so points and signals can be operated safely. Hence, axle counters are the backbone of modern train detection systems.

Thales is a leader in this technology and our SIL4 axle counter system – Az LM – is trusted all over the world. We are also pioneers: Thales was the first to explore the principle of using two magnetic fields (rather than one) to detect train wheels, an innovation that contributes to the extraordinary reliability of our axle counter system.   

Today, more than 150,000 of our wheel sensors are safeguarding railways around the world – a number which increases by 12,000 every year. Our axle counter systems can be found on all types of railways, including high-speed lines, main lines, metros, Light Rail Transit (LRT) and trams.

How do our customers benefit?

Thales’ Az LM system offers the highest availability in the market, which is why customers choose it for projects where the highest level of availability is vital. Deployments include high-speed lines in Germany and the Netherlands, Switzerland’s Lötschberg and Gotthard Base Tunnels, and Denmark’s nationwide ETCS Level 2 programme.

Maximum availability and scalability

Our Az LM system can be precisely configured to match our customers’ operational goals. In addition to the standard 2oo2 (two-out-of-two) system, we offer a 2oo3 system architecture and multi-redundant system architectures. This is unique in the market and offers the highest level of availability.  

Fault tolerance

The railway environment is harsh. Equipment is exposed to vibration, dust, heat, cold and moisture, so fault tolerance is essential. Az LM is designed with maximum resilience in mind, with features that include fault suppression, fault tolerant data transmission and automatic fault correction via meta sections. 

Low lifecycle costs

Az LM reduces costs in three ways. First, it minimises the use of copper cabling: all components of our axle counter system can be connected using IP connections. Second, Az LM incorporates self-diagnostics making it almost maintenance free. Finally, the solution is highly robust thanks to our unique slimline sensor technology. This contributes to reliability and reduces the risk of disruption penalties. 
Training: we provide a complete training package to support our customers’ ambitions. Everyone who uses Az LM – from signalling engineers and designers to maintenance staff in the field – has access to our comprehensive training and certification programme.


Az LM is “Cybersecured by Design” in the on-going development process, which means that security features are built-in to the design of the entire system. All Thales’ signalling solutions are continuously improved in accordance with ISO 27001 and NIST 800-53 security requirements.   

How is the solution evolving?

Nothing stands still in the world of railways and our axle counter system is no exception. Here are some examples of how Thales’ Az LM is evolving to meet new needs: 

Plug and play compatibility

Our axle counter system is designed in accordance with EULYNX principles on the standardisation of signalling interfaces. With infrastructure managers looking to centralise control in fewer interlockings, this is a vital capability: an existing Az LM system can be retained with low or zero adaptation when resignalling is carried out.

Big data applications

Axle counter systems generate a huge amount of data. The primary purpose of that data is to provide vital information to the interlocking. But axle counter data can be used in other ways as well.

First, it can be used in predictive maintenance solutions, such as Thales’ TIRIS solution. This can provide insights into the health of the axle counter system itself, as well as that of the rolling stock, making it possible to identify problems early.

Second, data from axle counters also has potential to keep trains running when signalling systems fail. In fact, this has already happened. Recently a leading national railway operator experienced a major failure, which meant that all the trains had to stop. To make matters worse, signallers were unable to see where the trains were on their workstations. What could be done?

Axle counter data was not affected by the outage. Because TIRIS captures the same axle counter location data as the interlocking, signallers were able to use TIRIS visualisations (which were still operational) to see where all the trains were. Thanks to this, it was possible to get the trains moving again, slowly and safely, before the failure was rectified and the system brought back online.

All of this underlines the power of digital data to support different operational scenarios – and to sometimes deliver unexpected benefits.