Development platform
TX4: active steering in the real world
The TX4, a modified Tram 2000 tram, is how Traila proved it.
Question
How do you prove an active-steering system on a real rail vehicle, not only in simulation?
What we did
Instrumented a real rail vehicle, TX4, with a purpose-built sensor suite
Designed and simulated an active-steering wheelset control system before it ever ran on the vehicle
Took the system from simulation to the vehicle on a Zurich test track, then iterated hardware and software through repeated field-test runs
What we measured
Vehicle dynamics and wear, in simulation and again in the field, at passive and active-steering settings, at more than one speed
Acoustic performance with a 48-channel acoustic camera, comparing the vehicle's architecture and active-steering on and off
Wheelset position, through inductive sensors and a position estimator, across repeated test runs
- 01
The test vehicle carried ten sensor types at once: rotary encoders, inductive position sensors, video cameras, accelerometers, laser-line scanners, a linear encoder, pressure sensors, speed sensors and strain gauges.
- 02
In simulation, active steering cut the total wear number of a rear bogie by 45%, across five curve radii from 16 to 76 m, modelled on a T2000 tram at each curve's maximum allowed speed in Zurich.
- 03
Field testing measured noise falling from 65.0 dBA to 61.5 dBA, comparing a conventional bogie to the active-steering axle.
- 04
Field testing ran on VBZ's public tram network as well as a closed test track, through switches, merges and crossings, on curves as tight as 18.5 m radius, at speeds up to 12 km/h.
- 05
Repeat field runs showed the inductive sensors detecting every track feature reliably, at speeds up to 12 km/h.
- 06
Simulation of the steering method kept wheel rise within half a millimetre in every case tested, at both 6 and 12 km/h.
- 07
TX4 is now retired; what the programme proved carries forward into next-generation vehicle development.
Origin
Traila's research reaches back to the mid-1990s.
Traila's research into the wheel-rail contact and vehicle dynamics reaches back to the mid-1990s. The strands include rotating-flange wheels, adaptive conicity and active-steering methods, all aimed at the same root cause: what happens where the wheel meets the rail.
Active steering, visualised
The interface, controlled versus not.
Traila built and tested the world's first sensor-based active steering system for urban rail, with thousands of kilometres on the TX4 in Zurich. The interface could be controlled, not just observed. That research continues into the vehicles of tomorrow.
Active steering
The origin story, and where it goes next.
Active steering is where Traila started. A test campaign in Zurich ran the TX4, a test vehicle, now retired: a decommissioned T2000 retrofitted with the active-steering bogie and a measurement suite. Zurich is where the vehicle ran, not a customer.
The work continues in a next-generation vehicle programme with academic and industry partners, taking the root cause into the vehicles of tomorrow. More to be announced.
Silence by design.
By actively aligning wheelsets to the rail path, the steering technology eliminated misalignment: cutting curve noise, structure-borne vibration, and wheel squeal in the TX4 test campaign. The acoustic camera made that reduction visible, comparing a conventional bogie against the active-steering axle.
By partnering with local operators, leading rail engineering consultants, and specialists in our niche areas of interest, we ensure that our solutions are deeply aligned with the operational realities and needs of the rail industry.
Simulation validates the model
Multi-body simulation, checked against the track.
Traila's laser-scan algorithms continuously refined the simulation environment and validated sensor data through the TX4 test campaign. Built on three years of real-world data from the TX4 test vehicle, now retired, the models replicated actual vehicle dynamics with high accuracy: even in curves, the wheel flange stayed contact-free, with multibody simulation results aligned with on-track measurements from Zurich.
Using advanced co-simulation tools such as SIMPACK and ABAQUS, Traila develops cost-efficient solutions that precisely predict the dynamic behaviour of actively steered rail vehicles, in full compliance with international safety standards.
Heritage · simulation
What the active-steering work showed, in simulation.
These are historical active-steering results from the origin research, largely simulation-based. They are heritage figures, not conditioning field results, and not a current-product claim. The conditioning field results assessed for the Swiss Federal Office of Transport sit on the proof page, separately, because they describe a different mechanism.
In simulation: up to 94% wear reduction, twice the wheel and infrastructure lifespan, a threefold reduction in acoustic noise, and more than 100,000 km simulated.
Heritage, active-steering, simulation results. Not conditioning field results and not a current-product claim. The field results assessed for the Swiss Federal Office of Transport are on the proof page.
Patents and publications
The intellectual property behind the work.
Seven active patent families across active steering, friction, monitoring and localisation. The research is peer-reviewed and conference-published.
Capabilities
Six disciplines, one test vehicle.
Sensors and laser scans: We are specialists in various sensor technologies, and our engineers develop new and interesting ways to apply advanced sensing for active steering positioning, track scanning and simulations improvement and validation.
HIL, SIL and digital twins: Our state-of-the-art Hardware and Software in the Loop (HIL & SIL) systems combined with digital twins provide an unparalleled testing and validation platform. These virtual replicas of our hardware enable us to optimise performance across countless situations before deployment. This accelerates development and ensures the highest precision and safety for our active steering systems.
Multi-body simulation and vehicle dynamics: Using the industry standard SIMPACK® we can predict how our system works, and ensure that our solutions work in a variety of vehicles and configurations.
Control system development: Our control systems are built to interpret complex sensor inputs. Through rigorous testing and continuous improvement, we ensure our solutions are both innovative and practical for everyday use.
Mechanical design: Real world testing of simulated solutions is the only way to prove our systems work in all situations. Our engineers are experts in turning ideas and concepts into reality.
Field testing: Field testing is crucial for validating our innovative active steering solutions. At Traila, we had a dedicated test tram, enabling us to conduct rigorous real-world trials. This hands-on approach allows us to refine our technology under actual operating conditions, ensuring reliability, efficiency, and safety.