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Content archived on 2024-04-16

RDS Advice and Problem Location for European Road Traffic


This project seeks to establish internationally accepted standards in RDS-TMC (Radio Data System - Traffic Message Channel) location coding, messages and message management and to obtain a real consensus among broadcasters, national traffic authorities and manufacturers through a liaison group structure with EBU, ECMT and national traffic authorities. This structure will permit the consistent operation of RDS-TMC throughout Europe. The project includes the development of both broadcast and in-vehicle test procedures and equipment.
The advice and problem location for European road traffic (ALERT) protocol specifies driver information messages and defines the message list, its structure and content, and its presentation to the driver. Traffic message control (TMC) messages are language independent and can be presented in the language of the user's choice. Standard messages provide the following 5 basic items of explicit, broadcast information:
event description, giving details of the weather situation or traffic problem, for example, and its severity;
location, indicating the area, highway segment or point where the source of the problem is situated;
extent, identifying the adjacent areas, segments or specific point locations also affected by the incident;
duration, giving an indication of how long the problem is expected to last;
diversion advice, showing whether or not drivers are recommended to find an alternative route.

Optional information can be added to any standard message using one or more additional data groups.

The research aimed at establishing internationally accepted standards in radio data systems (RDS) traffic message channel (TMC) coding, format and operation for use as part of a road traffic information system. Within the research, current proposals for single sequence and multisequence messages were reviewed and evaluated in order to reach a starting consensus for experimental evaluation. The standard protocol for approval had to be comprehensive, to ensure that all required locations and messages could be coded, flexible, to deal with the situations existing in many different countries and to allow the system to adapt to future changes, efficient (ie using a minimum necessary number of bits).

The main points to emerge were:
at the European Broadcasting Union (EBU) recommended RDS deviation level of +/- 2 kHz, RDS TMC appears to be viable as a means of conveying traffic information;
at lower RDS deviations reception reliability is reduced, although it may be possible to provide a useful service;
TMC messages should be kept short so that the majority of messages can be encoded as single groups;
message repetition is the preferred form of error correction at the transport level;
in multigroup messages no advantage is gained by transmitting the separate elements of a message contiguously in time;
no false messages were detected when message validation depended on 2 or more message transmissions.

The radio data system (RDS) is a means of broadcasting digital information by using some of the spare capacity available in the existing frequency modulation (FM) broadcasting system. RDS provides a silent, digital channel which can be added to any FM radio station. A primary objective of this research was to bring together all the national traffic messages developed to date to establish an agreed international set. The research led to a protocol for a traffic message channel (TMC) and a RDS TMC structure offering the flexibility needed for covering a full range of European traffic situations, while retaining the potential benefits of single group messages for the majority of actual events. The protocol increased the efficiency of the message coding. In conjunction with revised location codes, it allowed the great majority of messages to be broadcast using a single RDS group. The few multigroup messages containing additional, detailed information would be compatible with the recommended one group structure, through the use of virtually identical fields in the first group.

A standardized system for providing detailed up to date traffic information to motorists is paramount in an integrated road transport environment to assist in solving growing congestion problems. The ability to provide this information in a language of the driver's choice would enhance still further effectiveness of such a system. The research carried out in the RDS ALERT project addressed the above issues of standardization. A European standard for transmitting traffic messages using the radio data system traffic message channel (RDS TMC) has been developed. RDS TMC will permit a quantum jump in traffic data dissemination into the vehicle by several orders of magnitude over conventional spoken warnings on the radio. By linking TMC to on board navigation systems, an additional tool will be created for direction and guidance of traffic movements.

In developing a European TMC standard, both technical and political considerations were taken into account. These included the quality of available data, the needs as perceived by broadcasters and traffic experts, and the technical limitations of the RDS broadcast medium. Field trials were carried out to examine RDS reception across Europe and a diverse range of conditions were encompassed. The results have been used to evaluate each TMC protocol element in order to refine and optimize the final standard.
The technical approach comprises the following stages:
- identification of traffic-related message content together with associated structures, protocol and message management techniques;
- the carrying out of mobile RDS reception tests to gather data on error-statistics, especially in areas of severe multipath interference;
- the computer evaluation of the error-statistics to establish an empirical model;
- the establishment of a standard interface specification for the transfer of TMC data to other traffic-related technologies.
The project is subdivided into the following workpackages:
- Review and evaluate progress to date in achieving consensus
- Define and establish liaison group structure
- liaise with interested parties
- develop, discuss and finalize location codes
- review message repertoire and propose input methods for broadcasts
- define assessment criteria and scenarios
- develop, test and evaluate software message decoding
- develop, test and evaluate message management strategies
- finalize the technical appraisal and optimize protocols
- prepare Interim Standards for RDS-TMC throughout Europe
- consensus building and revisions to Interim Standard
- prepare proposal for Final Standard
Main Deliverables:
Report on guidelines for location coding, message sets, development of software to generate broadcast messages, development testing and evaluation of receiver message decoding, field tests, draft supplement to EBU RDS specification.


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Castle Rock Consultants Ltd
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Heathcoat Building Highfields Science Park
NG7 2QJ Nottingham
United Kingdom

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