A new series of specifications is born: S04

We are pleased to announce that a preview version of a new specification series is now available for Strategic and Principal members, thanks to the sustained effort from the ITxPT community. This milestone introduces support for system architectures built around an MQTT broker – marking an important step in the evolution of interoperability specifications, enabling a data-centric approach.

What is it designed for?

The new series aims to support system designs where data exchange is streamlined through a central broker. This architecture enables greater flexibility, real-time communication, and reduced integration complexity – key advantages in managing modern fleets and digital services.

  • Access the data sources and sync without writing your own protocols
  • Easily access your data remotely from a single implementation

Who can access these new S04 specifications?

The S04-MQTT broker based specifications preview was approved on 11 June 2025 by the Executive Board and is now available for review and testing for Strategic and Principal members, who are invited to provide feedback as we move toward a broader release in 2026 (01 October 2025: Associated members). This collaborative phase is essential to ensure the specifications are aligned with operational needs and industry expectations.

Strategic and Principal member have access in the ITxPT collaborative area, in the TC / Chestnut / S04 workspace.

S04: a series of specifications based on MQTT

The Strategic and Principal members have early access to this preview release for 6 months – starting 01 July. Associated members for 3 months – starting 01 October.

This 6-month timeframe enables Strategic and Principal members to build tests, run a proof of concept (either individually or joined with other members — see the PoC page) and provide feedback from the field to improve the specifications before they go public.

Note that a preview specification is not ready for tendering and not disclosable to external companies.

  • S04POO – General Rules
  • S04P01 – AIS
  • S04P02 – MQTT Broker
  • S04P03 – Journey Monitoring
  • S04P04 – Logon
  • S04P05 – Passenger Counting
  • S04P06 – Vehicle location

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If you would like to join the active ITxpt community and contribute to future ITxPT specifications, contact us for more information.