Vol. I · A field notebook
Notes on cooperative-ITS — written slowly, in plain text.
Everything here through the V2X lens: positioning, in-vehicle networks, the software-defined vehicle, sensor fusion, PKI, and how any of it gets deployed, funded and regulated. Only what matters once vehicles start talking to each other and to the roadside.
Recent entries
The EU and US V2X stacks share one number space ITS-AID and PSID are the same field, revised jointly in 2010. The real divergence is which fields are mandatory, where extensibility lives, and whether a timestamp carries confidence.
China's V2X plan to 2030: vehicle-road-cloud and C-V2X direct The 15th Five-Year Plan sets China's V2X architecture and radio. Its quantified targets cover the vehicle; roadside and connectivity carry no numbers.
What happens after a vehicle is reported in C-ITS Catching a false V2X message is half the job. ETSI TS 103 759 specifies the pseudonymous report and how it reaches the authority. Enforcement waits.
The BTP port registry: the real count of C-ITS messages Nine acronyms get all the coverage. The BTP port registry in ETSI TS 103 248 assigns 26 ports to 28 message types, and one changed hands since 2024.
ETSI C-ITS, Release 1 to Release 2: a standards map Which ETSI document is current for each C-ITS layer and message, and which one it replaced. A Release 1 to Release 2 map, with version numbers.
measurementDeltaTime: the age of every object in a CPM Every object in a CPM carries an age accumulated down a sensor and fusion pipeline. measurementDeltaTime declares it; ignore it and you draw the past.
The CPM confidence field that TS 103 324 never pins down Every object in a CPM is an offset from the sender's pose, and that pose is wrong twice over. TS 103 324 never settles whether the confidence covers it.
The message that tells your car where to park, and what comes next ETSI's POIM (TS 103 916) broadcasts live parking availability to passing vehicles, inside a point-of-interest envelope with room for far more.
C-ITS architecture: four layers and two planes The European C-ITS stack is one diagram everyone redraws. Four horizontal layers, two vertical entities for security and management, and why those two refuse to be layers at all.
The cyclist can be sold a radio; the pedestrian only has a phone A bike brand put V2X in an e-bike, but the real adoption vector for vulnerable-road-user safety is shared micromobility: a fleet the city already licenses.