SNC-Lavalin’s IWT4 technology measures the dynamic contact forces between the wheel and rail.

Instrumented wheelsets are railway wheelsets that have been instrumented and calibrated so that they are capable of accurately measuring the dynamic contact forces between the wheel and rail. Typically, they are capable of measuring these forces in the vertical and lateral direction. SNC-Lavalin’s IWT4 technology can also measure forces in the longitudinal direction.

Application Areas

To date, instrumented wheelsets have played a critical role in ensuring that the vehicles that we put on track are not susceptible to derailment. They also ensure that the vehicles don’t cause excessive track wear and damage. In the USA, Europe, China and Japan, standards for vehicle acceptance testing - such as EN14363 - require instrumented wheelsets to be used. The technology has also been used, albeit to a lesser extent, for research and development purposes, such as optimising bogie designs and increasing axle loads.

To date, instrumented wheelsets have mainly been used for rolling stock applications. However recent developments of the IWT4 technology have made it a powerful tool for examining the track. By measuring at very high frequencies, IWT4 is able to examine the condition of the track while travelling at regular linespeeds at regular axle loads, under a regular vehicle. We believe there is a massive potential for IWT4 to help railways better manage their track maintenance regimes.

The IWT4 Technology

We pioneered the use of instrumented wheelsets in the 1950s. The new generation of technology, IWT4, follows on from our IWT3 product.

  • IWT4 utilises the standard wheelsets fitted to the vehicle. No special “test wheels” are required. This simplifies project logistics, reduces the delivery time, and lowers the cost of the total measurement system.
  • Only one side of the wheel needs to be instrumented. This simplifies the instrumentation process and enables the system to be adapted to fit challenging bogie designs.
  • An advanced telemetry system removes the need for slip ring devices. This decreases costs, increases reliability, and simplifies installation of the system.
  • No destructive machining of the wheelset is required, so the structural integrity of the wheelset is preserved. This reduces risk and removes the need for additional periodic ultrasonic inspections.
  • Power is delivered to the system using an inductive transmission system, so as long as the vehicle is powered up, so are the IWT4s.

We have been applying IWT4 technology for clients around the globe since 2007, with over 60 wheelsets produced to date. While it is a ground-breaking product, it’s also robust and field hardened.

For more information, refer to our Frequently Asked Questions.

For a multimedia introduction to IWT4, view our demonstration video.

Contact Us


Jonny Beatty
Group Commercial Manager
+44 (0) 207 105 3719

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