The Hard Part of Connected Traffic is Making the Data Understand Each Other
Hamburg’s traffic signals were already producing the data. The problem was making more of it useful.
A proof of concept involving the City of Hamburg, Hamburg University of Applied Sciences, Yunex Traffic, TraffGO Road and Monotch has explored how existing real-time traffic signal information can be exchanged between systems and reused for connected mobility applications.
At the centre of the exercise was Signal Phase and Timing, or SPaT, data generated by traffic signal controllers across the city. Monotch connected its Traffic Live Exchange platform, TLEX, to a SPaT cloud supplied by Yunex Traffic, allowing the project partners to exchange and visualise the information and demonstrate applications based on it.
The exercise sounds relatively straightforward. Traffic signals produce data, a platform consumes it and applications use the resulting information. What happened during the integration reveals one of the less visible engineering problems facing connected transport systems: two systems can follow the same standards and still require considerable work before they properly understand one another. That problem becomes more consequential as cities move from isolated intelligent transport projects towards networks involving thousands of vehicles, signals, roadside units and applications.
Briefing
- Hamburg tested how existing real-time SPaT traffic signal data could be exchanged and reused through the TLEX platform.
- The proof of concept involved the City of Hamburg, HAW Hamburg, Yunex Traffic, TraffGO Road and Monotch.
- Local differences in Hamburg’s MAP and SPaT implementations had to be understood during integration despite the use of established standards.
- Hamburg plans to prepare up to 600 intersections and equip 2,000 buses for ITS-based bus prioritisation by 2030.
- The project points towards an increasingly important C-ITS challenge: making existing infrastructure data interoperable enough to support multiple applications.
The Data Was Already There
SPaT messages describe the current state and expected timing of traffic signal phases. Used alongside MAP data describing the geometry and topology of an intersection, they allow another system to determine which signal applies to a particular lane or movement and when that phase is expected to change.
ETSI specifications explicitly link the two. MAP information provides the intersection topology needed to relate SPaT information to the relevant lanes, while the SPaT message communicates the state and timing of the signal phases.
That combination creates some obvious applications. A connected vehicle can potentially know that a signal ahead will turn red before reaching it. A bus can receive information about remaining green or red time. Traffic management applications can use the same information without installing another sensor simply to discover what the signal controller already knows.
Hamburg’s proof of concept concentrated on extracting more value from that existing information. TLEX was connected to the Yunex Traffic SPaT cloud, with the data then used for real-time exchange, a dashboard and a demonstration application. The project also demonstrated how information including time-to-red and time-to-green could be made available for exchange and visualisation.
Nils Gayer, Project Lead at the City of Hamburg, said: “What impressed us was how straightforward it was to connect systems and share data, while maintaining very low latency. The PoC demonstrated how smoothly real-time data exchange can work in practice and gave us a clearer view of its potential for connected mobility in Hamburg.”
For HAW Hamburg, the project also provided research material. The university used traffic signal information to compare inputs from different sources and investigate the data behind them.
When Standards Meet Real Streets
Hamburg’s existing infrastructure reflected earlier engineering decisions and local implementations. Connecting the systems required Monotch to understand how the city structured its MAP data and encoded its SPaT information.
A technical standard can define how information should be represented and exchanged without guaranteeing that every system encountered in the field will have implemented every element in precisely the same way. Infrastructure makes the problem particularly persistent. Traffic controllers are not consumer electronics replaced every few years. Cities operate equipment installed at different times, supplied by different manufacturers and configured for local requirements.
New digital platforms therefore have to meet the network that actually exists rather than an idealised version of it. ETSI’s specifications provide the common framework, but real deployments still have to reconcile configuration, interpretation and legacy engineering choices before information becomes reliably interchangeable.
Joachim Wahle, Managing Director of TraffGO Road, said: “Connected mobility only works if technology fits the reality on the ground. By combining our knowledge of the German market with Monotch’s TLEX technology, we were able to show Hamburg what can already be done with the C-ITS data available today.”
TraffGO Road provided local market knowledge and coordinated stakeholders during the proof of concept, while Monotch supplied the data-exchange platform and interoperability work. Existing infrastructure can acquire new capabilities when the information it already produces becomes accessible outside the system for which it was originally created.
Hamburg’s Larger C-ITS Programme
The proof of concept sits within a much larger transition taking place across Hamburg’s road network.
The city is preparing to replace parts of the communications architecture currently used for bus priority at traffic signals. Hamburg says its existing arrangements rely partly on analogue radio frequencies that are due to become unavailable in their present form in 2028, while the digital radio alternative lacks the flexibility required for the next generation of mobility systems.
Its ITS-CUBE programme is developing the architecture for a C-ITS-based replacement. The programme has received approximately โฌ1.94 million through the European Investment Bank’s ELENA programme, with Hamburg working towards ITS-based bus prioritisation at as many as 600 intersections and compatible equipment on 2,000 buses by 2030.
An experimental connection between a traffic data platform and an existing SPaT source can tolerate specialist engineering attention. A city-wide system involving hundreds of intersections, multiple generations of equipment, thousands of vehicles and numerous applications needs repeatable ways of handling those differences.
Hamburg has already moved beyond the conceptual stage. Through C-Roads Germany 3, 100 traffic lights and 700 VHH Mobility buses are being equipped with ITS-CUBE technology as part of a โฌ20 million investment programme, with a 50% co-financing rate. The programme is intended to take the technology beyond test environments and onto public roads.
Hamburg has also described a system in which buses can receive information including door-closing and departure recommendations as well as remaining red and green times, allowing drivers and control systems to adjust movements through the network.
A Data Layer Above the Road
Monotch positions TLEX as a real-time data-sharing layer between road infrastructure, vehicles, applications and other data networks. Hamburg provides a useful test of that proposition because much of the physical infrastructure already exists.
A traffic signal controller generates information for its primary job of operating an intersection. Once that information can be exchanged reliably, the same data stream can potentially feed a bus-priority system, a connected vehicle service, a traffic management application or another system developed later.
Nicolas Mercier, Deployment Manager at Monotch, said: “The exciting part is that the data is already there. TLEX helps make that data usable across different systems and shows how one real-time data stream can support multiple connected mobility use cases.”
Each additional application does not necessarily require its own sensing layer or independent communications architecture. More of the engineering work instead falls on interfaces, data models, latency, governance and compatibility with existing assets.
Few transport authorities have the luxury of rebuilding an urban traffic network around a single technology stack. Connected mobility has to evolve while conventional traffic management continues operating beneath it.
From Connected Equipment to Connected Infrastructure
C-ITS has spent years demonstrating communication between vehicles and infrastructure, hazard warnings, public transport priority and information about signal states. At city scale, those capabilities have to operate across old and new controllers, different communications technologies, multiple software platforms and systems installed under successive generations of standards.
Hamburg’s experiment provides a small demonstration of how that transition may happen. Rather than discarding existing infrastructure because its implementation differs from a newer architecture, an exchange layer can interpret the available information and make it usable elsewhere.
There are limits to what a proof of concept establishes. The Hamburg exercise demonstrates technical integration and applications using existing traffic signal data; it does not by itself establish the economics, resilience or operational performance of such an architecture across an entire city. The next stages of Hamburg’s C-ITS programme will provide a more demanding test as deployments move onto public roads and the number of participating signals and vehicles grows.
If that expansion works, the most valuable component may not be another intelligent traffic signal or connected bus, but the ability to allow infrastructure installed at different times, for different purposes and by different suppliers to participate in the same real-time system. For cities with decades of transport technology already sitting beside and underneath their roads, that offers a more practical route towards connected mobility than starting again.
Key Industry Questions
- What is SPaT data?ย Signal Phase and Timing data describes the current state of traffic signal phases and information about when those phases are expected to change.
- What does MAP data provide?ย MAP data describes the topology and geometry of road infrastructure such as an intersection. It allows systems to associate signal information with the appropriate lanes and vehicle movements.
- Why are SPaT and MAP used together?ย Signal timing has limited value to a connected vehicle unless the vehicle can determine which signal phase applies to its lane or intended movement. MAP provides that spatial relationship.
- What did the Hamburg proof of concept test?ย It connected Monotch’s TLEX platform with Hamburg traffic signal data supplied through the Yunex Traffic SPaT cloud and demonstrated real-time exchange, visualisation and applications based on the information.
- Why can systems using the same standards still have interoperability problems?ย Standards provide common specifications, but deployed systems can reflect different versions, configurations, interpretations and historic implementation decisions. Integration may therefore require those local differences to be understood and accommodated.
- What is Hamburg’s ITS-CUBE programme?ย ITS-CUBE is developing Hamburg’s future C-ITS architecture for applications including bus prioritisation at traffic signals, replacing communications technologies that are becoming unsuitable for future requirements.
- How large could Hamburg’s C-ITS bus-priority deployment become?ย Hamburg is working towards ITS-based prioritisation at up to 600 intersections and compatible equipment on 2,000 buses by 2030.
- Does connected mobility require replacing existing traffic infrastructure?ย Not necessarily. The Hamburg proof of concept examined how information already generated by existing traffic signal infrastructure could be exchanged and used by additional applications.
Strategic Takeaways
- Existing traffic infrastructure can become more useful when its operational data is accessible to systems beyond its original application.
- Standards provide a common framework, but deployed infrastructure still contains local implementations that integration layers must accommodate.
- Large C-ITS deployments will depend heavily on data architecture and interoperability alongside roadside hardware.
- Reusing reliable real-time data across multiple applications could reduce duplication of sensing and communications infrastructure.
- Hamburg’s expansion towards hundreds of intersections and thousands of buses will provide a more demanding test of how well this approach scales operationally.
