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Requirements and System Specification for Dynamic Traffic Messages


The main objective of this project is to define a methodical and systematic approach to the problem of the distribution of information to drivers through roadside infrastructures both in urban and extra-urban environment.
The survey carried out on European variable message sign (VMS) systems currently in use provided a rich source of information and permitted the real state of the art to be assessed. Analysis of this survey identified the following key aspects of VMS application: system objectives, strategies adopted, message presentation and content, display technologies, detection and information collection, data handling and processing and system assessments.
An analysis was made of road operators' objectives for using VMS and the definition of measures of effectiveness (MOE) used in assessing them. The major conclusions of this exercise were that the few systems that had been subjected to a quantitative analysis, were found to be successful but to varying degrees, and that VMS system development in general could benefit from homogenous and systematic operational and socioeconomic analyses of the effectiveness and impacts of advanced VMS systems. By means of the survey and its consequent analysis, the project was able to identify the exemplary features of some of the most successful systems currently in use. The final recommendations of the project were based partly on the observance of current successful practices and partly on the modelling and simulation work performed during the research and development stage of the project.
The following 5 application fields were identified to provide a framework for the analysis of the objectives and information requirements for VMS systems: motorway section, motorway interaction with other roads, motorway network, urban route choice and rural signalling and warning. These 5 application fields conveniently cover not only the different types of roads or environments (motorways, other extraurban and rural roads, urban roads), but also the basic elements of a network (intersection or node, section or link, network). Hence any suitable scenario for VMS application could be classified under one of these fields. The application field framework w as also used during the development and recommendation phases of the work. Simulation models were identified and developed for these fields, and specific architectural, operational and ergonomic recommendations were made on the basis of the results achieved and of the analysis of current practice.

Studies of existing variable message sign (VMS) systems show a clear trend towards systems that are less dedicated to a particular objective or strategy. More versatile displays are now being used that are able to show a wider variety of message and that sometimes incorporate more than one type of technology on the same sign. It is therefore possible to identify a process of functional and technological integration within the VMS application domain. For the superdomain of the entire road transport environment, a similar process of integration has been identified. In this superdomain, VMS constitutes one of many road transport informatics (RTI) technologies that may be effectively combined to achieve major improvements in road safety, traffic efficiency and environmental control.
The project investigated the potential for further integration both within the VMS domain and within the larger domain of the integrated road transport environment (IRTE). Practical innovative recommendations were made for combining traffic control functions on a single sign and for combining VMS with advanced in vehicle technologies.
Considerable effort was devoted to developing system concepts and architectures for VMS systems that would integrate functions or applications (eg weather related warnings, road closures, diversions, lane allocation) and that would remain open to include the operation of other technologies. Attention was focused on the extraurban application fields.
A general requirements analysis was made for the extraurban application fields in order to identify specific problems encountered, to assess the effectiveness of currently available variable message sign (VMS) measures, to determine what and how much information is needed to enable an efficient application of VMS measures and to determine the technical requirements for system architectures, roadside data acquisition and processing and message display elements. Extraurban control strategies were surveyed and the m ost significant influencing factors and boundary conditions were identified. In the case of motorway network control in particular, appropriate estimation and prediction methods for improving the control strategies of route guidance systems were pointed out. Diversion strategies were tested on a simulation of a motorway/secondary road network situated to the north of Munich. The main 3-lane motorway route through this network is often congested and vehicles are required to divert onto another 2-lane motorway or onto a 1-lane secondary trunk road. The simulated network was constructed specifically for the purposes of the project. Traffic simulation was carried out by the macroscopic model SIMONE.
Aspects of driver behaviour affecting the operational effectiveness of VMS constitutes an important open research area. A behavioural model was developed to assess driver response to speed limitations imposed by VMS. The model was based on experiments made on a stretch of motorway in the Federal Republic of Germany and was incorporated in the SPEACS simulator. Driver behaviour was observed for simulation of a vehicle population of 1000.
A prototype was made available on 25/08/92

System concepts and architectures were developed for specific applications according to the envisaged needs of the user. The information, processing and general technical requirements for implementing the recommended system architectures and concepts were analysed and reported for 5 application fields. Specifically for the extraurban application fields, architectures and concepts were developed for 3 scenarios: high capacity motorways surrounded by low capacity secondary roads, motorway route guidance and rural signalling and warning.
In the first scenario special considerations regarding data sources, control elements and variable message sign (VMS) control strategies were made and the requirements for implementing the following measures were examined: traffic diversion, recommendation of an alternative route, warnings on motorways of unfavourable or dangerous conditions and traffic diversion from secondary roads to the motorway.
For the second scenario the characteristics of subsystems constituting a motorway route guidance system were examined and presented. The following subsystems were identified: data acquisition subsystem, data processing subsystem, display subsystem, data transmission subsystems and energy supply subsystem.
The following types of VMS system and typical measures were identified for the third scenario: section control systems (speed control, overtaking prohibitions, traffic and weather related warnings), warning systems (eg fog, black ice at particularly dangerous spots), speed control systems at critical points (eg town entrances, narrow bends), diversion systems (eg closing of steep gradient sections in the event of snow or ice) and parking information systems (eg at tourist sites). A systematic analysis ofrequirements for a modular, hierarchical VMS system architecture was made. This entailed an outline of the essential system levels, the identification of input data requirements and of the required system components for data acquisition and transmission and for power supply. General functional requirements and operational constraints were set. The general requirements analysis produced during this phase would provide a useful basis from which specifications can be derived for the design of any foreseeable VMS system for use in the extraurban environment.
A set of general recommendations for appropriate technologies for implementing the proposed strategies and architectures has been prepared. Recommendations were made according to the application field. A set of principles were also proposed for coping with general operating problems such as hardware maintenance, fault and error tolerance. Recommendations were made for effective VMS location, for the use and composition of text messages, appropriate pictograms and sign features.
The issue of integrating VMS within the new integrated road transport environment (IRTE). Scenarios were suggested that would feature the integration of VMS with in vehicle technologies.
The project's recommendations have been summarised in the WHITE BOOK for VMS applications. This document has now been distributed to about 200 road operators, manufacturers and other experts involved in the design, installation and operation of VMS systems.
A strategy for displaying information in the context of the future general IRTE will be developed. At present it is envisaged that roadside infrastructures for displaying information will still be used but will become increasingly `intelligent'. The `intelligent' road signs will display credible information and warnings which will be regularly updated on the basis of information from other RTI systems like traffic flow data from a route guidance service.
The scope of the project includes on-board driver information equipment and research will define what information needs to be provided by these. Since the project deals with dynamic traffic messages it may also investigate and assess to what extent different ways of providing information influence behaviour and traffic control strategies.
To date standardization activity in this field has been devoted to producing standards for signs and pictograms. At present no European standard exists for Variable Message Signs (VMS). Another objective of the project is therefore to begin standardization work by specifying the requirements for information exchange between roadside VMS and drivers. In particular a minimum level of and degree of relevance of information has to be defined.
The project is closely aligned to the objectives of the "Extra-urban Signalling and Communication Systems" task. The goal is the study and the definition of control and information systems for private and public traffic on inter-urban roads and in rural areas.
Main Deliverables:
Recommendation for the use of dynamic traffic messages.


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10126 TORINO

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Participants (7)