The ITxPT collaborative community publishes new technical specifications for an MQTT broker-based architecture
We are pleased to announce that the broker-based ITxPT S04-MQTT specifications, previously available only to members, are now accessible to the general public via the ITxPT Documentation Centre.
If you do not have an access yet, you can request one here.
This new series of specifications introduces the concepts and key features required to support an MQTT broker–based Architecture. It covers several functional areas – including journey monitoring, vehicle location, and many others. It was initially released as a preview for ITxPT members in June 2025. Its public release is the result of a comprehensive review process, incorporating six months of feedback from ITxPT members following the preview release, as well as insights gathered from Proof‑of‑Concept projects conducted by principal and strategic members.
A broker‑based architecture offers a more secure, flexible and efficient communication framework that better meets the evolving needs of modern public transport systems. By enabling seamless data exchange both within vehicles and between vehicles and central back‑office systems, it supports a wide range of use cases – from service monitoring and operational optimisation to maintenance, asset management and statistical analysis. This approach ensures the delivery of reliable, up‑to‑date passenger and operational information, while the use of MQTT removes traditional barriers between on‑board systems and back‑office infrastructure. With MQTT v5 providing robust, built‑in security mechanisms, broker‑based solutions offer a future‑proof foundation for scalable, interoperable, and secure data communication across the entire transport ecosystem.
A staged public release begins on 1st April 2026, following free registration.
The first batch, comprising the following items, is now available:
- S00- General Architectural Requirements v1.0.0 [S04 related]
- S04P01- Active Inventory Service Overview v1.0.0
- S04P01N01- AIS Topics and Processes v1.0.0
- S04P01N02- AIS Data Definitions v1.0.0
- S04P01N03- AIS Formal Requirements v1.0.0
- S04P02N01- MQTT broker v1.0.0
- S04P02N02- MQTT Client v1.0.0
Find more details below on the full set of S04 series, including the release schedule for each part.
| S00- General Architectural Requirements v1.0.0 [S04 related] | 01-Apr-26 |
| S04P01- Active Inventory Service Overview v1.0.0 | 01-Apr-26 |
| S04P01N01- AIS Topics and Processes v1.0.0 | 01-Apr-26 |
| S04P01N02- AIS Data Definitions v1.0.0 | 01-Apr-26 |
| S04P01N03- AIS Formal Requirements v1.0.0 | 01-Apr-26 |
| S04P02N01- MQTT broker v1.0.0 | 01-Apr-26 |
| S04P02N02- MQTT Client v1.0.0 | 01-Apr-26 |
| S04P02N03- MQTT bridging v1.0.0 | 13-May-26 |
| S04P03- Journey Monitoring v1.0.0 | 29-Apr-26 |
| S04P04- Logon v1.0.0 | 27-May-26 |
| S04P05- Passenger Counting v1.0.0 | 29-Apr-26 |
| S04P06- Vehicle Location v1.0.0 | 15-Apr-26 |
| S04P06N01- VL GNSS Data v1.0.0 | 15-Apr-26 |
| S04P07– Ticketing Overview | 27-May-26 |
| S04P07N01- Validation Counting | 27-May-26 |
Your feedback remains essential for improving future versions of the specifications. We encourage you to share your comments and suggestions via the ITxPT Change Request Platform, to help us refine and develop the specifications moving forward.
For more information – or to join our active and collaborative ITxPT community – please visit our website or contact us directly.
Collaboration between our members is at the heart of ITxPT, and it is through this cooperation that new versions of the specifications are developed and delivered as part of structured release packages.
