Zurich Public Transport standardizes brake testing with TMX
How VBZ tests more than 230 trams with one standardized system.
Zurich Public Transport (Verkehrsbetriebe Zürich, VBZ) is one of the largest municipal transit operators in Switzerland. Its more than 2,800 employees carry over 300 million passengers a year. The backbone of the network is 15 tram lines with around 250 rail vehicles that cover more than 14.4 million kilometers annually. At this scale, regular brake testing to regulatory requirements is a core element of vehicle safety.
About 500 brake tests a year at four sites
VBZ runs about 500 brake distance tests on its trams every year in its three depots and the central workshop. These tests are required after major maintenance and are part of ongoing quality assurance.
To improve these measurements further, VBZ looked for a new brake distance measurement system for all sites. The main goal: standardized procedures and equipment. The system had to deliver the required accuracy, meet the requirements of the Swiss Federal Office of Transport (FOT), and still allow custom setups, especially for in-depth analysis at the central workshop.
Clear hardware and software requirements
VBZ set requirements for both hardware and software. On the hardware side, the focus was on precise sensors that work reliably in any weather and on any track surface, mount and dismount easily, and come with rugged, portable data acquisition in a carrying case, including battery operation without external power.
On the software side, platform independence was key: the solution had to run on Windows, iOS, and Android. It also had to cover all measurements required by the FOT, support custom test scenarios with individual limits, and generate documentation and reports at the push of a button.
Michael Fink, responsible for the depots, summed up the requirements: VBZ needed a solution it could rely on in any weather, on any surface, and on any vehicle type. And it had to be intuitive enough for technicians to focus on the measurement, not on operating the system.
Philipp Humbel, quality and systems engineer at the central workshop, added: besides a standard solution for compliance tests in the depots, quality assurance also needed the flexibility for more extensive analysis, with the option to define custom test scenarios while staying compliant.
The solution: TMX BrakeTest system with OMS sensor
VBZ chose a complete solution: the OMS 4 optical sensor from Sensoric Solutions combined with the TMX BrakeTest system, which consists of a compact DAQ case and the TMX BrakeTestApp.
The OMS 4 is an optical-inertial distance sensor with a speed measurement non-linearity below ±0.1 % FS. It works without satellite reception. The supplied magnetic and suction-cup mounts allow flexible mounting: on the side of the cab with the suction cup, or protected under the vehicle with the magnetic mount.
The TMX DAQ case holds the complete data acquisition in a rugged, portable enclosure. The built-in battery allows operation without external power, and the system is ready within seconds of power-up. Devices connect wirelessly over Wi-Fi.
The TMX BrakeTestApp runs on Windows, iOS, and Android and manages templates for vehicles and brake tests. Templates created once for specific vehicle types or test scenarios can simply be selected. The app then guides the user step by step through the entire test: measurement with live speed display, automatic evaluation against defined limits, and PDF report generation.
Custom adaptations for VBZ
TMX adapted both hardware and software to VBZ. The trigger inputs accept 24 to 80 V and cover every trigger voltage in the fleet. The software templates were tailored to VBZ requirements for speed, brake distance, and deceleration. Other adaptations include a live plot window for the measurement data, a manual trigger as an alternative to automatic trigger detection, VBZ-specific metadata in the data acquisition, and a PDF layout in VBZ corporate design.
From mounting to acceptance in four hours
Commissioning took place on December 17, 2025, at the central workshop. Hands-on training started with sensor mounting and hardware setup, followed by an introduction to the software on the VBZ staff's iPads. Then the VBZ technicians took over: they ran several predefined brake tests at different speeds and with different brake types, set up their own test scenarios with individual limits, and tried different sensor mounting positions.
As a final test, they generated a PDF report and emailed it from the iPad straight to the office for documentation and filing in SAP. By 11:45 a.m., commissioning was complete.
Eight identical systems for all sites
VBZ now operates eight identical TMX brake distance measurement systems: two for each of the three depots and two for the central workshop.
What matters most to VBZ is that depots and central workshop use the same procedures and equipment, with standardized test sequences and consistent results. VBZ also benefits from the accuracy and reliability of the optical sensor, simple mounting, intuitive iPad operation with live speed display, automatic PDF reports sent directly by email, and the flexibility to create custom test scenarios for quality assurance.
From the field
Philipp Humbel, quality and systems engineer at the VBZ central workshop, points to the combination of accuracy and flexibility: the optical sensor delivers reliable, compliant measurements regardless of weather or environment, while the software gives the team the freedom to build its own test scenarios. For quality assurance, he says, that is the right balance between compliance and adaptability.
Michael Fink, head of tram maintenance at VBZ, notes how quickly the team adopted the system: operation on the iPad is intuitive, and the live display makes the work easier and safer. Automatic report generation in particular saves a lot of time. From test to documentation in SAP, it is now one continuous, efficient process.
Download the report
Read the full reference report on the VBZ project with all technical details and photos (PDF, in German):
More information
Learn more about the TMX BrakeTest system: