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BS EN ISO 14819 — ITS: RDS-TMC Traffic and Travel Information Coding
Intelligent Transport Systems — Traffic and Travel Information Messages via Traffic Message Coding Series
🚗 The BS EN ISO 14819 series is a set of British Standards implementing the European standard EN ISO 14819 in the field of Intelligent Transport Systems (ITS), specifying the coding of traffic and travel information based on RDS-TMC (Radio Data System — Traffic Message Channel) and the ALERT-C protocol. The series was prepared by ISO/TC 204 (Intelligent transport systems) and CEN/TC 278 (Road transport and traffic telematics), with UK participation entrusted to Technical Committee EPL/278 (Intelligent transport systems). RDS-TMC is the widely used FM-radio traffic information service in Europe, transmitting compressed traffic event information over a subcarrier superimposed on the FM broadcast, which in-car navigation receivers use to provide real-time traffic alerts and route guidance. The ICS classifications are 03.220.20 (road transport) and 35.240.60 (IT applications in transport).
💡 RDS-TMC encodes huge volumes of traffic information in very few bytes: events use event codes, locations use location tables, and direction and extent use extension codes. The three ISO 14819 parts (coding protocol, event codes, location referencing) have clear divisions of responsibility, letting broadcasters, navigation vendors and location-table maintainers each play their part.
1. Series Composition 📌
The series comprises three documents (2013 edition, superseding the 2003/2004 editions), corresponding to the coding protocol, event and information codes, and location referencing:
| Standard | Year | Title / Subject | Main Content |
|---|---|---|---|
| BS EN ISO 14819-1 | 2013 | Coding protocol for RDS-TMC using ALERT-C | Data format, message structure, repetition and update rules, decoding rules |
| BS EN ISO 14819-2 | 2013 | Event and information codes for RDS-TMC using ALERT-C | Event/information categories and code allocation (accidents, congestion, road works, etc.) |
| BS EN ISO 14819-3 | 2013 | Location referencing for RDS-TMC using ALERT-C | Location tables, locative location numbers and referencing methods |
⚠️ Edition continuity: the 2013 edition supersedes the 2003/2004 editions. When upgrading an RDS-TMC broadcast system or adapting in-car terminals, verify compatibility of event codes and location tables between old and new editions.
2. RDS-TMC Coding Protocol (Part 1) 📡
Part 1 specifies the coding protocol for RDS-TMC using ALERT-C, defining the coding structure of traffic messages: single-group and multigroup messages, system information, location information, event and direction extensions, and so on. The protocol specifies repetition and update strategies for messages (e.g., repeating every 3–5 minutes, holding when unchanged), ensuring receiving terminals can assemble complete messages even under weak signal or packet loss.
3. Event and Information Codes (Part 2) 📋
Part 2 specifies the event and information codes for RDS-TMC, defining the quantifier codes used to describe traffic status categories and event codes: accidents, congestion, road works, weather, hazards, restrictions and so on each have a standard code. Combined with the Application List, these codes give broadcasters and receivers a unique, consistent understanding of the same event, supporting multilingual broadcasting and interoperability between operators.
4. Location Referencing (Part 3) 🗺️
Part 3 specifies the location referencing for RDS-TMC, defining the structure of location tables, location numbers and referencing methods. Location tables consist of country/regional tables and internal tables, dividing the road network into numbered location points (e.g., junctions, service areas, road segments). A traffic event references a location number for precise positioning without transmitting full geographic coordinates.
🚨 The usability of TMC messages depends on accurate maintenance of coding and location tables. Misused event codes, outdated location numbers or inconsistent location-table versions cause receiving terminals to display incorrect information or navigation errors. Location tables must be updated as roads change and kept version-synchronised.
5. Engineering Practice and Deployment 🛠️
- 🔍 Broadcast operation: traffic information broadcasters generate and periodically repeat TMC messages per the coding protocol, ingesting data from traffic management centres.
- 📋 Terminal adaptation: in-car navigation and mobile apps parse TMC messages, resolve event locations using location tables and trigger voice/visual alerts.
- 🏗️ Location-table maintenance: national location-table authorities maintain road network location data and publish updates for downstream users.
- 📊 Interoperability testing: run conformance tests on the encode-decode chain per the standard to ensure interoperability between vendors’ equipment.
6. Frequently Asked Questions ❓
❓ Q: What is RDS-TMC?
A: RDS-TMC is a traffic information channel transmitted over the RDS subcarrier of FM radio; traffic events are compressed and encoded for broadcast, and in-car navigation receivers display real-time traffic conditions and alerts after reception.
A: RDS-TMC is a traffic information channel transmitted over the RDS subcarrier of FM radio; traffic events are compressed and encoded for broadcast, and in-car navigation receivers display real-time traffic conditions and alerts after reception.
❓ Q: What is ALERT-C?
A: ALERT-C is the message coding and protocol system used by RDS-TMC, defining the coding structure, repetition strategy and update rules for traffic messages; the ISO 14819 series standardises it.
A: ALERT-C is the message coding and protocol system used by RDS-TMC, defining the coding structure, repetition strategy and update rules for traffic messages; the ISO 14819 series standardises it.
❓ Q: How does TMC locate an event without transmitting coordinates?
A: TMC uses location tables to number the road network; the event message carries a location number (locative) rather than geographic coordinates, and the receiver resolves the specific segment and direction using the same version of the location table.
A: TMC uses location tables to number the road network; the event message carries a location number (locative) rather than geographic coordinates, and the receiver resolves the specific segment and direction using the same version of the location table.
🔍 Q: Why are TMC messages repeated?
A: Repetition counteracts FM interference and reception packet loss, ensuring terminals receive complete messages even under weak signal; when unchanged, periodic repetition is maintained per the standard to sustain validity.
A: Repetition counteracts FM interference and reception packet loss, ensuring terminals receive complete messages even under weak signal; when unchanged, periodic repetition is maintained per the standard to sustain validity.