JPL's Wireless Communication Reference Website

Chapter: Network Concepts and Standards

Road Transportation Informatics

The growth of road traffic and the increasing inconvenience and environmental damage caused by road congestion require a substantially more efficient use of the infrastructure for physical transport. In contrast to many measures taken in the past, advanced solutions will require a wireless 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 and personal telephony and wireless electronic mail, to mobile subscribers.

Figure: Electronic Toll Collection using Digital Short-Range Communication. Transactions are made in a few tens of milliseconds.
Courtesy: Bosch Telekom, Germany.

State of the Art: Europe

The first formalized transportation telematics program in Europe, PROMETHEUS (PROgraM for European Traffic with Highest Efficiency and Unprecedented Safety), originated in 1986 from the EUREKA project (EUropean REsearch Coordination Agency, an open framework for cooperation between European industry and research industries). Being initiated by the European automotive industry, PROMETHEUS first of all aimed at technological innovations on-board the car, formulated in four functional areas: improved driver information, active driver support, cooperative driving and traffic/fleet management. In 1988 the European Community launched DRIVE (Dedicated Road Infrastructure for Vehicle safety in Europe) as part of the Framework program. The aim of DRIVE was to establish an IRTE (Integrated Road Transport Environment) by means of increasing road safety, reducing the adverse ecological impact of road traffic, and improving the utilization of the road infrastructure using Road Transport Telematics (RTI). In 1992, DRIVE I, focusing on "exploring the options" was continued in the form of DRIVE II, or the Advanced Transportation Telematics (ATT) program, focusing on "preparing for implementation". This is to be followed in 1995/1996 by DRIVE III, focusing on "large scale pilot implementations", as part of the Fourth Framework. Recently, the umbrella organization ERTICO (European Road transport Telematics Implementation Coordination Organization) was established for coordination between the research in PROMETHEUS and DRIVE.

DRIVE distinguishes seven inter-related areas of major interest:

USA

In 1989 in the USA the Mobility 2000 group was formed and led to the formation of IVHS America (Intelligent Vehicle Highway Systems) in 1990, whose function was to act as a Federal Advisory Committee for the US Department of Transportation. In 1991 the Intermodal Surface Transportation Efficiency Act (ISTEA), of which the IVHS program was defined as an integral part, became law in order to develop 'a national intermodal transport system that is economically sound, to provide the foundation for the nation to compete in the global economy, and to move people and goods in an energy-efficient manner'. In 1994 the IVHS program was renamed into ITS (Intelligent Transportation Systems) indicating that besides car traffic also other modes of transportation receive attention.

ITS distinguishes six inter-related system areas:

Compared to the seven areas of major interest in DRIVE a striking lack of interest in Demand Management within ITS is noticed. Another contrast between both transportation telematics strategies is that establishing an universal system architecture has been an initial key feature of the ITS program.

Japan

A car ownership of 95 percent and a small geographical area of which only 20% is inhabitable necessitated Japan to deploy transportation telematics already in the 1950s. The lack of overall coordination of applying transportation telematics in Japan has not only led to the development and implementation of a respectable number of such applications by various governmental and industrial organizations, but also to a situation in which this large diversity of applications is not able to support or to co-operate with one other. For instance, in 1973 the Ministry of International Trade and Industry (MITI) funded the Comprehensive Automobile Control System (CACS), in 1984 the Ministry of Construction (MOC) and the governmental Highway Industry Development Organisation (HIDO) funded the Road/Automobile Communication Systems (RACS), and also in 1984 the Ministry Post and Telecommunications (MPT) conducted the Advanced Traffic Information and Communication System (AMTICS). All these systems aimed at similar objectives and were more or less competitive. In the early 1990s the need for national coordination and standardization and international collaboration was recognized and AMTICS and RACS were effectively combined in the Vehicle Information and Communication System (VICS), and comprehensive programs such as Advanced Traffic Information Services (ATIS), Advanced Road Traffic Systems (ARTS) and Super Smart Vehicle System (SSVS) were introduced. Recently, in 1994, the VEhicle, Road and Traffic Intelligence Society (VERTIS) was established for the purpose of integrating international liaison work in the field of transportation telematics (which is comparable to the European ERTICO organization).

With respect to operational implementations of transportation telematics, Japan is indisputably far ahead of both Europe and the USA: about 1/3 of the circa 135,000 signalized intersections in Japan are under central computer control, almost all large metropolitan areas are provided with video camera's and ultrasonic technology connected to traffic information boards and variable message signs, in over 75 metropolitan areas traffic management centers are operational, and about 400,000 in-car navigation systems have been sold.

Advanced Systems: ATM/IS

In order to achieve an optimal utilization of the existing transportation system, the authorities strive to alleviate the prevailing car-caused problems by means of coordinating physical flows of road traffic. In addition, they take into account preserving accessibility and environment as well as enhancing road safety. These processes take place at a given demand for road traffic, that is assumed to be fixed in time and place (i.e., no demand management). As far as the above- mentioned aims are concerned, we distinguish two classes of involved information systems Moreover, Advanced Traveler Information Systems (ATIS) are relevant to individual drivers.

Advanced Traffic Management Systems (ATMS)

The class of Advanced Traffic Management Systems (ATMS) is area-oriented and concentrates on a (certain part of a) road network (e.g. congregated sections of the freeway network or parts of the urban or the rural network). The traffic performance on the remaining (parts of the) road networks are considered to be of less interest for ATMS. For the concerning area, ATMS aim at an optimal traffic performance at system level, which might be expressed as serving as many cars on the concerning road network, dissipating a minimum total travel time. In this way, ATMS strive for a system optimum.

To achieve a system optimum, ATMS require relevant information about the actual system performance on the entire road infrastructure under consideration. Only in this way, ATMS can dynamically adjust or distribute the actually offered traffic to or over the available infrastructural capacity by means of traffic management measures. The information about the actual status of the traffic (and the infrastructure) should be available in real-time (e.g. in time intervals of 1 to 5 minutes) and concerns traffic data that is aggregated to a certain extent. An important characteristic of ATMS applications is that decisions are made and measures are (seen to be) implemented by traffic managers in the traffic center, which complete the collected external data collections with know-how gathered by training and experience.

Since the administrators of ATMS applications are the road authorities, which are also responsible for the road infrastructure, an ATMS monitoring system is obviously based on fixed traffic detectors that are mounted in, above or along the road infrastructure. We will refer to this type of detectors as infrastructure based traffic detectors. As a consequence of the network-wide oriented nature of ATMS, an ATMS monitoring system using fixed, infrastructure based traffic detectors (e.g. inductive loops) is characterized by rather large detector spacings (typically of 5 to 10 kilometers. Shorter distances between the detectors would make such a network-wide monitoring system financially prohibitive.

A typical example of an ATMS application is Incident Management, which deals with swiftly detecting disturbances in the traffic flows, estimating expected delay, determining spare capacity of the remaining road links and proportionally distributing traffic over the entire network.

Advanced Traffic Control Systems (ATCS)

Advanced Traffic Control Systems (ATCS) serves as 'executive complement' to the class of Advanced Traffic Management Systems (ATMS). ATCS are local-oriented and concentrate on certain parts of the road infrastructure (i.e., critical or notorious bottlenecks, such as bridges, tunnels and on/off ramps). For these local sites, ATCS aim at an optimal traffic performance at local level. This might be expressed as serving as many of the offered cars as possible in a time period that is as short as possible, so dissipating a minimum total time loss. In this way, ATCS strive for a local optimum.

The instruments belonging to the class of ATCS are more or less rigid standard operations, which can be fully automated and need no human intervention. Hence, according to the definition of information systems given before, ATCS constitute no true information system (the component 'persons' is not involved). The exact objectives of the particular ATCS can be modified by the corresponding ATMS, for instance by adjusting certain parameters. The complexity of computer models and the calculation speed of computers restrict area-wide application of ATCS, because computations and actions need to be performed in real-time. The data collections for ATCS should be very accurate, possibly relate to individual vehicles and be directly available in real-time (e.g. in intervals of several seconds to 1 minute).

As a consequence of the local oriented nature of ATCS, an ATCS monitoring system exclusively concerns the direct vicinity of the corresponding (ATCS) traffic control system and basically only provides traffic data for this control system. Moreover, only fixed, infrastructure based traffic detectors (e.g. inductive loops) with very small detector spacings (typically of some hundreds of meters) will be suitable. Since ATCS applications concern only a very limited geographical area, these detector spacings are financially affordable. Longer distances between the detectors, or utilization of non-infrastructure based traffic detectors is not eligible as this can only provide data with a accuracy and a reliability that will be too low for ATCS.

A typical example of an ATC system application is ramp metering, which deals with gradually allowing vehicles on the on-ramp to enter the freeway, depending on the proportion between the actual flow and capacity of the freeway. Almost all traffic systems that are currently employed belong to the class of ATCS applications.

Advanced Traveler Information Systems (ATIS)

Where the road authorities aim at achieving an optimal utilization of 'their' transportation system, in general, road users may be assumed to be predominantly interested in accomplishing an optimal route from their origin to their destination over this infrastructure (user optimum). This might be expressed in a minimal travel time (or a minimal generalized time, so comprising the actual or perceived travel time, traveled distance, et cetera) for their entire trip. The third class of applications of transportation telematics that we distinguish, the class of Advanced Traveler Information Systems (ATIS), supports the road user in achieving this task. Hence, the core objective of ATIS is to provide each road user with the information he or she needs to achieve his or her specific travel objectives, within the limiting conditions dictated by the various ATMS and ATCS applications. In this way, ATIS strive for several individual users optima.

For the purpose of supporting and achieving several individual users' optima, ATIS require information about complete routes from origin to destination, about delays on the regular route, about the travel time on alternative routes and about alternative ways of available transport, at the moment of passage. This implies that specific parts of different networks (urban, rural and state) that are relevant during a specific trip are of interest, with information about delays on routes at the moment they will actually be used (requiring short term predictions) instead of instantaneous information. Hence, the regular traffic information to be obtained for ATIS purposes may become available every rather long time interval of for instance 5 to 15 minutes (incidents should be reported more swiftly). These characteristics are in sharp contradiction to the information requirements of ATMS applications, which demand predominantly actual (i.e. real-time) information about one, but entire network.

As a consequence of the established characteristics of ATIS information, i.e. both area-wide and concerning several networks that cover each entire route, an ATIS monitoring system can not always practically be based on fixed, infrastructure based traffic detectors. In particular installing fixed traffic detectors in an entire urban road network, requiring extremely short detector spacings due to the close-meshed urban road infrastructure, would be unrealistic. Furthermore, in consideration of the opposite objectives of ATMS and ATIS, an ATIS monitoring system should preferably be independent of an ATMS monitoring system and preferably be based on anything but infrastructure based traffic detectors exploited by government or state. For these specific ATIS purposes, one can use a monitoring system based on non-infrastructure based detectors, such as probe vehicles. These are normal vehicles that participate in the traffic flow, are equipped with a location and communication device and accordingly transmit experienced traffic data to a traffic center.


Photo: Screen of Philips CARIN navigation system.

A typical example of an ATIS application is Dynamic Route Guidance, which deals with guiding the individual car driver whose vehicle is equipped with such a DRG-device, from its origin to its specified destination, along the best route (e.g. shortest in time), according to real-time traffic situations.

Transportation and electronic industries and (conjoint) car manufacturers develop, operate and administrate the ATIS applications, whereas their (indirect) goal is a commercial one, that is to make profit with a product for which the consumer is willing to pay. Besides, also transportation authorities pay attention to transportation telematics applications which are destined for providing road users with actual traffic information (such as variable message signs, VMS). We gather these latter telematics applications among the class of ATMS, as their principal aim remains optimizing the existing transportation infrastructure, either directly by means of deploying measures or indirectly by means of disseminating information. This means that also the information provided by ATMS is first of all aimed at this objective and is not necessarily optimal for each individual road user.

Photo: Philips car radio system, displaying traffic information about the A12 motorway in Holland.

ATIS systems may make use of systems for Traffic Information Datacasting, such as RDS.

Traffic Flow Models

Three elementary traffic parameters are commonly considered in traffic information, management and control systems, namely, the traffic density, traffic flow and traffic speed. Estimates of the current situation, historical data and prediction of near-future behavior are used in ATMS, ATCS and ATIS systems.

contents next Glossary

JPL's Wireless Communication Reference Website Marcel Westerman and 1993, 1995.