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en_alt:c-its [2026/08/10 11:59] – Image sizes and wording (review feedback) hajoen_alt:c-its [2026/09/08 08:34] (current) – [Further reading] idahoenigmann
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 ===== Message types ===== ===== Message types =====
  
-Several standardised message types travel over C-ITS. These are the ones that matter in practice.+Several standardised message types travel over C-ITS. The message contents are specified by ETSI. Machine readable message specifications are published as ASN.1 files (https://forge.etsi.org/rep/ITS/asn1).
  
-^ Type ^ Full name ^ In one sentence ^ +All messages share a common header. This header includes the messageId, which specifies the type of message. 
-| [[en_alt:c-its#cam|CAM]] | Cooperative Awareness Message | Periodic status broadcast from a vehicle | + 
-| [[en_alt:c-its#denm|DENM]] | Decentralized Environmental Notification Message | Warning about an exceptional situation | +^ Message Id ^ Type ^ Full name ^ In one sentence ^ 
-| [[en_alt:c-its#mapem|MAPEM]] | MAP Extended Message | The geometry of an intersection | +| 1 | [[en_alt:c-its#denm|DENM]] | Decentralized Environmental Notification Message | Warning about an exceptional situation | 
-| [[en_alt:c-its#spatem|SPATEM]] | Signal Phase and Timing Extended Message | The current state of a traffic light | +| 2 | [[en_alt:c-its#cam|CAM]]   | Cooperative Awareness Message | Periodic status broadcast from a vehicle | 
-| [[en_alt:c-its#ivim|IVIM]] | Infrastructure to Vehicle Information Message | Road sign and infrastructure information |+| 4 | [[en_alt:c-its#spatem|SPATEM]] | Signal Phase and Timing Extended Message | The current state of a traffic light | 
 +| 5 | [[en_alt:c-its#mapem|MAPEM]] | MAP Extended Message | The geometry of an intersection | 
 +| 6 | [[en_alt:c-its#ivim|IVIM]] | Infrastructure to Vehicle Information Message | Road sign and infrastructure information | 
 +| 9 | SREM | Signal Request Extended Message | Request message for green light at intersection | 
 +| 10 | SSEM | Signal request Status Extended Message | Reply message to SREM | 
 +| 14 | CPM  | Collective Perception Message | Sensor information | 
 + 
 +Other, less common, message types are: 
 +  * VRU Awareness Message (VAM), 
 +  * Point of Interest Message (POIM), 
 +  * Parking Information Message (PIM), 
 +  * Interference Management Zone Message (IMZM), 
 +  * Service Announcement Essential Message (SAEM), 
 +  * Electric Vehicle Charging Spot Notification (EVCSN), 
 +  * Electric Vehicle Recharging Spot Reservation messages (EV-RSR), 
 +  * Maneuver Coordination Message (MCM), 
 +  * Marshalling Infrastructure Message (MIM), 
 +  * Marshalling Vehicle Message (MVM) 
 + 
 +While ETSI defines the structure of C-ITS messages and their permitted value ranges, some values remain open to interpretation—for example, a role may be represented as an integer without specifying what a value such as 42 actually means. ETSI can also be vague about when and how often messages should be transmitted, sometimes specifying only a broad range such as 1–100 Hz. 
 + 
 +C-Roads (https://www.c-roads.eu/), an EU-funded platform for harmonising C-ITS, addresses these ambiguities. It defines concrete use cases, specifying which messages should be sent, how information should be modelled within those messages, which values to use, and under what conditions and frequency messages should be transmitted.
  
 ==== CAM ==== ==== CAM ====
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   - Vehicle length and width   - Vehicle length and width
   - Status of the lights, e.g. indicators, low beam, rear fog light   - Status of the lights, e.g. indicators, low beam, rear fog light
 +
 +The specification for message content is given by ETSI EN 302 637-2 and ETSI TS 103 900.
  
 Since 2019 more and more cars have been equipped with C-ITS and transmit this data, as long as Car2X is enabled in the vehicle's menu. This is the data we use to draw vehicles on the map: Since 2019 more and more cars have been equipped with C-ITS and transmit this data, as long as Car2X is enabled in the vehicle's menu. This is the data we use to draw vehicles on the map:
  
-{{:cam2.png?440|Vehicles on the live map, drawn from CAM messages}}+{{:cam2.png?0x420|Vehicles on the live map, drawn from CAM messages}}
  
 ==== DENM ==== ==== DENM ====
  
-DENMs are **event-driven** warning messages (ETSI EN 302 637-3). While CAMs are broadcast continuously, a DENM is only sent when something exceptional happens, and it is repeated for as long as the event is valid.+DENMs are **event-driven** warning messages (ETSI EN 302 637-3 and ETSI TS 103 831). While CAMs are broadcast continuously, a DENM is only sent when something exceptional happens, and it is repeated for as long as the event is valid.
  
 Typical triggers: Typical triggers:
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 IVIMs are sent by RSUs, for example along the ASFINAG motorway network. Unlike a DENM, an IVIM applies to a defined section of road rather than to a single point. IVIMs are sent by RSUs, for example along the ASFINAG motorway network. Unlike a DENM, an IVIM applies to a defined section of road rather than to a single point.
  
 +===== Further reading =====
 +
 +Background on the technology and on the policy behind it. Sources for individual deployments are listed with the regions themselves, on [[en_alt:coverage|Coverage]].
 +
 +  * [[https://de.wikipedia.org/wiki/C-ITS|Wikipedia: C-ITS]] (German)
 +  * [[https://www.bmimi.gv.at/themen/mobilitaet/alternative_verkehrskonzepte/telematik_ivs/publikationen/citsstrategie.html|Federal Ministry: C-ITS strategy for Austria]]
 +  * [[https://c-its-deployment-group.eu/activities/c-its-deployments/|C-ITS Deployment Group: C-ITS is now ready for use in Germany]] (04/2021)
 +  * [[https://www.its-viennaregion.at/|ITS Vienna Region]] — the ITS competence centre for Vienna, Lower Austria and Burgenland
 +  * [[https://www.youtube.com/watch?v=G2VGzrJVO2Q|Video: How to Improve Public Transport with C-ITS — Vienna]] (05/2026)
 +  * [[https://www.c-roads.eu/|C-Roads: The European C-ITS Platform]] - EU-funded harmonization of C-ITS
en_alt/c-its.1786355995.txt.gz · Last modified: by hajo