JPL's Wireless Communication Reference Website

Chapter: Network Concepts and Standards
Section: Road Transportation Informatics

Communications for Road Traffic Informatics

The growth of road traffic and the increasing inconvenience and environmental damage caused by road congestion require better use of the infrastructure for physical transport. Over the last few years it has become clear that Advanced Traffic and Transportation Management and Information Systems (ATM/IS), Commercial Vehicle Operations (CVO) and Automated Vehicle Control Systems (AVCS) will require a communications infrastructure for vehicles communicating with roadside base stations and vice versa and with other (nearby) vehicles. This will require extensive use of mobile radio communication, in addition to the present desire to extend conventional services, such as cellular telephony and wireless data services, to mobile subscribers. Efficient use of the available radio spectrum and effective management of the tele-traffic appears essential.

Applications and Services

Electronic Toll Collection

Traffic Information Datacasting

In Europe, the Radio Data System (RDS) uses digital data signals which are inaudibly inserted into the FM-program on the same subcarrier frequency as ARI, but now pan-European, and the Radio Data System-Traffic Message Channel (RDS- TMC), that will use RDS capacity for transmitting digitally coded traffic messages to vehicles, requiring a dedicated TMC receiver to language-independently decode the messages.

Furthermore, in Britain CARFAX is being used, while in German speaking countries from around 1974 we find the Autofahrer Rundfunk Information (ARI), that alerts drivers for an upcoming traffic information broadcast, and ARI aufgrund Aktueller Messdaten (ARIAM), which uses automatic incident detection devices to reduce the elapsed time between observing and reporting traffic disturbances.

In the USA, Highway Advisory Radio (HAR) is operational, which is a special short-ranged radio that spatially localizes traffic information messages, using dedicated amplitude modulation (AM) transmitters located at the roadside, and Advanced Highway Advisory Radio (AHAR), which is a more advanced version of HAR, which provides an automatic interrupt when an advisory message is available.

Future Systems

The European road authorities collaborate within the European Conference of the Ministers of Transport (ECMT), in the Sub Working Group on Road Vehicle Communication. This group cooperates with broadcasters and manufacturers to coordinate the development of systems for traffic information distribution, such as RDS-TMC. The ECMT Sub Working Group works on standardizing European communication protocols for the message distribution or exchange, and the coding of location references.

One objective of the road authorities is to optimize of the use of existing road networks and to mitigate congestion. Interestingly, a system-optimum use of the road infrastructure, as desired by the road authority, may differ from advising the shortest and fastest route for each individual motorist.

The "ALERT C" protocol uses messages standardized as an extension of the EBU "Catalogue of Events". It was developed under the DRIVE I programme. It provides among other things,

A traffic advisory system involves

Migration to a Dedicated Communication Architecture

The network architecture and transmission standard for Intelligent Vehicle Highway Systems are topic of current discussions. One approach is to use existing technologies, preferably even existing communication services. Some other approaches aim at a dedicated infrastructure for IVHS, with its own frequency allocation. As an IVHS application for a spectrum allocation will compete with similar requests from many other new services, it is unlikely that a new band can be allocated to IVHS without a detailed plan for the services and applications to be supported, an architecture for the network and estimates of the teletraffic loads.

Whether the lower-layer communication services are best provided by a single, uniform radio access technique, suitable for any propagation environment and for any set of services, or, alternatively through multiple radio networks, each developed to offer only a selected set of data transport services is not a problem unique to IVHS. It is unclear whether multiplexing different categories of teletraffic onto the same spectrum resources leads to a substantial trunking gain in wireless networks. This is in contrast to the situation in cable or fiber-optic backbone (ISDN) links, where installation and maintenance cost is the essential motivation for integration. Nonetheless, there is clear need for wireless systems that can offer integrated services, even though hybrid, non- uniform radio access techniques might be used. Nonetheless, a dedicated IVHS communication infrastructure has several advantages over a hybrid communication architecture using existing systems.

Further Reading


Printable Documents

Literature

  1. J. Walker (Ed.), "Mobile Information systems", Artech House, London, 1990.
  2. M.P. Ristenblatt, "Communication architectures for the Intelligent Vehicle Highway Systems are available", IEEE Veh. Soc. Newsletter, Vol. 39, No. 1, Feb. 1992, pp. 8- 19.
  3. A. Polydoros et al., "Vehicle-to-roadside communication study", USC, Los Angeles, 1992.
  4. More

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JPL's Wireless Communication Reference Website 1993, 1995.