Why doesn't C-ITS interoperate with DATEX II and the national access points?

They were built for different consumers and standardised by different bodies. C-ITS uses ETSI messages such as DENM over the air for vehicles in real time; DATEX II is an XML format that national access points use to publish traffic data to service providers; the Data for Road Safety ecosystem exchanges sensor data business-to-business. ETSI's own TR 103 903 states that the NAPCORE ecosystem does not use ETSI ITS standards but refers to standards from other bodies. Each satisfies the same EU obligation to share safety information by a different route.

What is the SRTI collaboration agreement?

In April 2024, six organisations, TISA, DATEX II, the Car-2-Car Communication Consortium, Data for Road Safety, NAPCORE and C-Roads, signed an agreement to harmonise the message sets used for Safety-Related Traffic Information. It is the clearest public admission that these ecosystems do not currently interoperate natively, since the parties would not need to harmonise message sets that already matched.

What EU regulation requires sharing safety-related traffic information?

Delegated Regulation (EU) 886/2013 covers safety-related traffic information; Regulation (EU) 2015/962 covers real-time traffic information. They mandate the outcome, that safety and traffic information be made available, without mandating a single interface, which is why several parallel systems can all be compliant at once.

Where is the hard part of bridging these systems?

In semantics and geography, not transport. Mapping a C-ITS DENM cause code to a DATEX II situation type and to a sensor-data record has no published normative equivalence, and the location models differ: ETSI uses a geographic reference position and networking areas while DATEX II uses linear referencing such as ALERT-C or OpenLR. Translating a hazard between them without losing or misplacing it is the unsolved work.

Is road-data fragmentation a bug or a market?

It is a structural feature of how European road data grew, and it is also a market. Every service that needs to work across borders or across ecosystems pays a translation tax today. The organisation that builds a reliable bridge between the tactical vehicle world and the strategic data world sits at the table where the harmonised message sets are being decided.

One hazard, three road-data worlds that don't talk to each other

Ice on the road exists in three separate European data systems that don't natively interoperate. Six organisations signed a paper in 2024 admitting it.

A gritting truck passes a sensor and reports black ice at kilometre 42. That single fact, one hazard at one location, now has to exist in at least three European data systems that do not natively speak to each other, each of them fully compliant with the same piece of EU law. The event is real and singular. Its representations are three, and they do not line up.

This is the quiet structural problem underneath a decade of connected-mobility announcements. The technology to move a hazard warning is solved many times over. What is not solved is that the hazard lives in incompatible worlds, and moving it between them loses information every time.

The three worlds

Europe grew three overlapping systems for the same job, each optimised for a different consumer:

World	Built for	Typical format	Signed
C-ITS (ETSI)	vehicles, tactical, real time	DENM, ASN.1 UPER over the air	yes, TS 103 097
Data for Road Safety (ERTICO)	business-to-business exchange	sensor-data records	no
NAPCORE / national access points	public open data	DATEX II XML	no standard mechanism

The C-ITS world is the one this blog usually lives in: a vehicle broadcasts a DENM, another vehicle acts on it in seconds, and the message is cryptographically signed so the receiver can trust it. The Data for Road Safety world is a business arrangement where carmakers and data providers pool hazard information and hand it back enriched. The national-access-point world is the public one, where each country runs an access point publishing traffic data as DATEX II for anyone building a service on top.

Three worlds, three formats, three trust models, three governance bodies. A fact that starts in one of them does not arrive in the others for free.

The bodies admit it themselves

It would be easy to dismiss this as an outsider’s complaint. It is not. The bodies that run these ecosystems have said so themselves, on the record.

ETSI’s own mapping document, TR 103 903, states plainly that the NAPCORE ecosystem does not make use of ETSI ITS standards but refers to standards from other bodies. And in April 2024, six organisations, TISA, DATEX II, the Car-2-Car Communication Consortium, Data for Road Safety, NAPCORE and C-Roads, signed a collaboration agreement to harmonise the message sets used for Safety-Related Traffic Information. You do not sign an agreement to harmonise message sets that already match. The signature is the confession.

Why it persists

The reason nobody simply fixed this is that the fragmentation is downstream of the law, and the law asked for an outcome rather than an interface.

Delegated Regulation (EU) 886/2013 requires that safety-related traffic information be made available. Regulation (EU) 2015/962 does the same for real-time traffic information. Neither one prescribes a single message set or a single access method, and for good reasons at the time: mandating one technology would have frozen the market and picked winners before the technologies were mature. So every ecosystem built its own compliant path, and each is genuinely compliant. The regulation got the outcome it asked for. It just got it three times, in three incompatible shapes.

Where the value actually sits

For anyone building in this space, the bridge is worth more than any of the three systems it connects, and it is also the hardest thing to build.

The difficulty is not moving bytes. It is semantics and geography. A C-ITS DENM carries a cause code and sub-cause code; DATEX II carries a situation record with its own taxonomy; the sensor-data world carries yet another. There is no published normative table that says this cause code equals that situation type, so every bridge invents its own and hopes it matches the next one. Worse is location. The C-ITS world describes where a hazard is with a geographic reference position and networking areas; the DATEX II world uses linear referencing along a road network, ALERT-C location codes or OpenLR. Translating “here” from one model to the other, without moving the hazard to the wrong lane or the wrong carriageway, is the part that quietly breaks.

Which is exactly why the six-organisation agreement exists, and exactly why it is not finished. Whoever can translate a hazard between the tactical vehicle world and the strategic data world, reliably and with the geography intact, is holding the piece everyone else needs and nobody has standardised.

The risk of moving first

There is a real hazard in building this ahead of the group. Publish a mapping before the SRTI harmonisation closes and it may diverge from the one the bodies eventually agree, leaving you with a bridge to nowhere. That is a genuine risk. It is also the reason to be in the room: the mapping that wins will be the one that was built, tested against real data, and brought to the table, rather than the one drawn on a whiteboard. The fragmentation is not going to resolve itself into a single system. The most likely future is not one world but a good enough translation layer between the three, and that layer is still unclaimed.

For the C-ITS side of this picture, the messages a vehicle actually broadcasts and what a DENM contains, start with the C-ITS message set tour.