Christina Diakaki

Review of road traffic control strategies

Traffic congestion in urban road and freeway networks leads to a strong degradation of the network infrastructure and accordingly reduced throughput, which can be countered via suitable control measures and strategies. After illustrating the main reasons for infrastructure deterioration due to traffic congestion, a comprehensive overview of proposed and implemented control strategies is provided for three areas: urban road networks, freeway networks, and route guidance. Selected application results, obtained from either simulation studies or field implementations, are briefly outlined to illustrate the impact of various control actions and strategies. The paper concludes with a brief discussion of future needs in this important technical area.

A MULTIVARIABLE REGULATOR APPROACH TO TRAFFIC-RESPONSIVE NETWORK-WIDE SIGNAL CONTROL

The paper presents the design approach, the objectives, the development, the advantages, and some application results of the traffic-responsive urban control (TUC) strategy. Based on a store-and-forward modelling of the urban network traffic and using the linear-quadratic regulator theory, the design of TUC leads to a multivariable regulator for traffic-responsive co-ordinated network-wide signal control that is particularly suitable also for saturated traffic conditions. Simulation investigations demonstrate the efficiency of the proposed approach. Results of TUCs first field implementation and evaluation are also presented. Finally, summarising conclusions are drawn and future work is outlined.

Traffic flow modeling of large-scale motorway networks using the macroscopic modeling tool METANET

This paper employs previously developed modeling, validation, and stimulation tools to address, for the first time, the realistic macroscopic simulation of a real large-scale motorway network. More specifically, the macroscopic simulator METANET, involving a second-order traffic flow model as well as network-relevant extensions, is utilized. A rigorous quantitative validation procedure is applied to individual network links, and subsequently a heuristic qualitative validation procedure is employed at a network level. The large-scale motorway network around Amsterdam, The Netherlands, is considered in this investigation. The main goal of the paper is to describe the application approach and procedures and to demonstrate the accuracy and usefulness of macroscopic modeling tools for large-scale motorway networks.

Extensions and New Applications of the Traffic-Responsive Urban Control Strategy: Coordinated Signal Control for Urban Networks

The objectives, approach, advantages, and some application results of recent extensions of the traffic-responsive urban control (TUC) strategy are presented. Based on well-known methods of the automatic control theory, TUC allows for traffic-responsive coordinated signal control of large-scale urban networks that is particularly efficient under saturated traffic conditions. The first version of the TUC strategy controlled only the green splits. After initial development and the first field implementations and evaluations, TUC was expanded to perform real-time cycle and offset control, and to allow for public transport priority. Simulation investigations of the extended TUC application in parts of the urban networks of Tel Aviv and Jerusalem, Israel, by use of the AIMSUN microscopic simulator demonstrate the high efficiency of the new signal control strategy.

Applications of the urban traffic control strategy TUC

Despite the long-lasting research and developments in the field of urban traffic control systems, the continuously increasing mobility requirements urge for solutions that will release urban areas from the serious congestion problems and their consequences. From the control point of view, this may be translated into the employment of traffic-responsive systems that respond automatically to the prevailing traffic conditions. This is the aim of the signal control strategy TUC, whose basic philosophy, design methodology, characteristics and application results under both simulated and field conditions are presented in this paper. Based on a store-and-forward type of mathematical modelling and using well-known methodological tools from Automatic Control Theory, the TUC strategy addresses in a simple but efficient way, as demonstrated from the applications so far, the problem of co-ordinated, traffic-responsive signal control in large-scale urban networks.

INTEGRATED TRAFFIC-RESPONSIVE URBAN CORRIDOR CONTROL STRATEGY IN GLASGOW, SCOTLAND: APPLICATION AND EVALUATION

The new integrated traffic-responsive urban corridor control strategy IN-TUC (integrated traffic-responsive urban control) is presented. IN-TUC was developed and applied to the M8 corridor network in Glasgow, Scotland, within the European Telematics Applications in Transport project Telematics Applications in Bavaria, Scotland, and Others. The aim of the strategy, which is built on the well-known methods of the automatic control and optimization theories, is to provide, at suitably defined constant control intervals, traffic-responsive settings for the various control elements included in a corridor network area. The results of the preliminary simulation investigations as well as the results of the field implementation and evaluation of the strategy seem promising both for the particular site and for integrated corridor control systems in general.

Simulation studies of integrated corridor control in Glasgow

Abstract The paper presents the work performed within the European DRIVE II Project EUROCOR (European Urban Corridor Control) in relation to modelling and integrated control of the M8 Eastbound Corridor in Glasgow. The main intention of the study was not the design of new control strategies but the investigation of the qualitative impact of various control measures such as ramp metering, route diversion via variable message signs and signal control, and of their integration under realistic conditions. To this end, several scenarios of included control measures were investigated using the macroscopic modelling tool METACOR (Modele d’Ecoulement du Trafic sur Coridor), demonstrating the issues and potential benefits arising from different levels of integration.

Simulation investigations of the traffic-responsive urban control strategy TUC

The paper presents the basic characteristics of TUC, a recently developed traffic-responsive urban control strategy. Based on a store-and-forward type of modelling and using well-known methods of the automatic control theory, the approach followed by TUC designs (off-line) and employs (online) a multivariable regulator for traffic-responsive coordinated network-wide signal control. Simulation investigations demonstrate the strategys high efficiency. Summarised conclusions are presented, and future work is outlined.

Application and Evaluation of the Signal Traffic Control Strategy TUC in Chania

The article presents results of a field implementation and evaluation of the traffic-responsive signal control strategy Traffic-responsive Urban Control (TUC) in two junctions of the urban network of Chania, Greece. Based on a store-and-forward modelling of the urban network traffic and using the Linear-Quadratic regulator theory, the design of TUC leads to a multivariable regulator for traffic-responsive coordinated network-wide signal control that is particularly suitable for saturated traffic conditions. The presented results, although limited in space (two junctions) and time of evaluation, are promising for the particular site and for the control of urban networks in general as they indicate a superior performance of TUC compared to an established signal control strategy.

TUC and the SMART NETS project

The new-generation, network-wide signal control strategy TUC (traffic-responsive urban control) has been first developed within the European Transport Telematics project TABASCO and later been improved and validated with further simulations. TUC is particularly designed for saturated traffic conditions, where other UTC systems are known to fail or perform poorly. TUC formulates a linear-quadratic optimal control problem based on store-and-forward mathematical modelling. Initial results from a small-scale field-application in Glasgow (Scotland) and the simulations carried out were so encouraging that TUC is now going to be applied and demonstrated on a large scale in the cities of Chania (Greece), Munich (Germany) and Southampton (UK) in the SMART NETS project, which is co-funded by the European Commission in the framework of their 5th Framework Programme of Research within the IST Programme.