PTX Specification Version 2.0: A New Industry Standard for the Use of V2X in Public Transport

Initiated by ebblo, then Trapeze, a group of leading operations control system and OBU manufacturers have jointly developed an interface that, for the first time, creates an open, manufacturer-neutral communication standard between C-ITS on-board units (V2X-OBU) and on-board computers (IBIS) in buses and trams.

The recently published PTX specification version 2.0 is an important milestone for public transport in Germany, Switzerland and Austria, as well as beyond. It forms the basis for a future-proof and cost-efficient infrastructure for the integration of C-ITS functions into public transport vehicles.

What is the PTX specification?

The PTX specification ensures that on-board computers and V2X OBUs from different manufacturers work together reliably. It currently supports the C-ROADS use cases ”PVD”, “TLP” and ”GLOSA”. The specification defines the messages that are exchanged between the OBU and IBIS via MQTT and provides the JSON schemas for this.

Why is the interface necessary?

Vehicles must communicate with each other and with municipal infrastructure to enable services such as traffic light preemption, green waves and safety warnings. Without a uniform interface, expensive isolated solutions are created. The PTX specification enables transport companies to implement and introduce standardised V2X-based functions quickly and cost-effectively.

What are the advantages for transport companies?

Transport companies benefit from numerous advantages when using the PTX interface:

• Competitive and transparent procurement – PTX enables manufacturer-neutral tendering, reduces dependencies and creates fair opportunities for comparison between offers.
• Lower integration costs and fewer risks – Standardised interfaces simplify integration, reduce engineering and maintenance costs, and make upgrades easier to plan.
• Flexibility throughout the entire life cycle – Thanks to modularity, systems can be modernised independently of one another, which reduces costs and protects investments in the long term.
• Future-proofing through open standards – Clear versioning and open governance ensure that PTX grows with new requirements – independently of individual manufacturers.
• Innovative and dynamic ecosystem – Open interfaces promote competition, facilitate market entry for new providers and accelerate the introduction of innovative solutions.

How did the PTX specification come about?

At the end of 2022, initial exploratory talks took place between ebblo, then Trapeze, and OBU manufacturers Herman and Yunex. A first draft version of the specification was already available in May 2023, and an initial presentation was given at the C-ITS Forum in February 2024.

Over time, the project group grew to its current seven partners. IVU joined in September 2024, INIT in March 2025, and consider-it and s.a.d. in August 2025.

In June 2025, a live demonstration based on PTX version 1 was presented to a broad audience during the Technical Visit in Hamburg on the occasion of the UITP. In autumn 2025, experts from the participating companies jointly revised the specification to integrate the experience gained and different use cases. Version 2.0 has been available since December 2025 and can be used for tenders.

Quote from Dominique Müller, Innovator and Product Manager at ebblo:
“With the PTX specification, we are establishing an open industry standard that offers transport companies genuine freedom of choice among OBU providers while also reducing costs in the long term. The close, constructive cooperation between all partners was a highlight for me.”

Who can use the interface?

The PTX specification is openly accessible and can be used directly in projects. Developers can find all the necessary documents and schemas, as well as information on governance and licensing, on the GitHub page linked below. Contributions and comments are expressly welcome in order to further develop the interface collaboratively.

Where can the PTX specification be found?

The link below will take you to the English-language GitHub page for the PTX interface. There you will find the specification, the schemas and other relevant documents. If you have any questions, please contact us directly.