Vägtrafikinformatik - Trafikantinformation - Meddelanden via Traffic Message Coding (trafikmeddelandekodning) - Del 1: Kodningsprotokoll i Radio Data System - Traffic Message Channel (RDS-TMC) för ALERT C (ISO 14819-1:2013)
1.1 General scope
The ALERT-C protocol is designed to provide mostly event-oriented road end-user information messages. Many "hooks" have been left for future development and a few status-orientated road end-user information messages were included.
The presentation section of the ALERT-C protocol specifies messages that may be presented to the user in accordance with the general requirements set out above. It defines the message structure and content, and its presentation to the end-user.
RDS-TMC messages are language-independent, and can be presented in the language of the user's choice. The ALERT-C protocol utilises a standardised Event List (ISO 14819-2) of event messages with their code values, which also includes general traffic problems and weather situations.
ALERT-C defines two categories of information within messages: basic and optional items. In principle, basic information is present in all messages. Optional information can be added to messages where necessary.
Standard RDS-TMC user messages provide the following five basic items of explicit, broadcast information:
1. Event description, giving details of road event situations, general traffic problems and weather situations (e.g. congestion caused by accident) and where appropriate its severity (e.g. resulting queue length).
2. Location, indicating the area, road segment or point location where the source of the problem is situated.
3. Direction and Extent, identifying the adjacent segments or specific point locations also affected by the incident, and where appropriate the direction of traffic affected.
4. Duration, giving an indication of how long the problem is expected to last.
5. Diversion advice, showing whether or not end-users are recommended to find and follow an alternative route.