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2018 | Buch

Freeway Traffic Modelling and Control

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This monograph provides an extended overview of modelling and control approaches for freeway traffic systems, moving from the early methods to the most recent scientific results and field implementations. The concepts of green traffic systems and smart mobility are addressed in the book, since a modern freeway traffic management system should be designed to be sustainable. Future perspectives on freeway traffic control are also analysed and discussed with reference to the most recent technological advancements

The most widespread modelling and control techniques for freeway traffic systems are treated with mathematical rigour, but also discussed with reference to their performance assessment and to the expected impact of their practical usage in real traffic systems. In order to make the book accessible to readers of different backgrounds, some fundamental aspects of traffic theory as well as some basic control concepts, useful for better understanding the addressed topics, are provided in the book.

This monograph can be used as a textbook for courses on transport engineering, traffic management and control. It is also addressed to experts working in traffic monitoring and control areas and to researchers, technicians and practitioners of both transportation and control engineering. The authors’ systematic vision of traffic modelling and control methods developed over decades makes the book a valuable survey resource for freeway traffic managers, freeway stakeholders and transportation public authorities with professional interests in freeway traffic systems.

Advances in Industrial Control reports and encourages the transfer of technology in control engineering. The rapid development of control technology has an impact on all areas of the control discipline. The series offers an opportunity for researchers to present an extended exposition of new work in all aspects of industrial control.

Inhaltsverzeichnis

Frontmatter

Introduction

Frontmatter
Chapter 1. Freeway Traffic Systems
Abstract
The efficient management of freeway traffic networks is a very crucial issue in all the developed countries, where advanced technologies and methodologies have been designed and are still under development in order to provide the users with a safe, sustainable, coordinated and smart traffic system. One of the main negative points experienced by travellers in freeways is surely the formation of congestion phenomena, but other related aspects must be taken into consideration, such as pollutant emissions, fuel consumption, safety and noise. This chapter investigates the main issues associated with freeway traffic systems and introduces some key concepts about the possibility of managing and controlling freeways in order to enhance the mobility of people and goods, paying attention to the new developments in information and communication technologies.
Antonella Ferrara, Simona Sacone, Silvia Siri
Chapter 2. Fundamentals of Traffic Dynamics
Abstract
Traffic flow theory is devoted to study the interactions between vehicles (or drivers) and the infrastructure, which is given by many components, such as the roadways, the road signs and the traffic control actuators. Traffic phenomena are very complex, since they depend on the interactions of a large number of inhomogeneous vehicles and on many external factors. The first attempts to develop a mathematical theory of traffic flow date back to about one century ago, and the technology advancement of the last decades (in computer processing capabilities, as well as in measurement devices) has further enabled the evolution of traffic flow theory. Nevertheless, the research in traffic flow modelling is still very active and different types of traffic models are nowadays available, both based on theoretical approaches and on empirical observations. Such models can be used by traffic managers to forecast traffic conditions, and consequently to properly inform users about the forthcoming traffic state they can encounter in their travel, or to adequately design the traffic control frameworks to be applied in freeway networks.
Antonella Ferrara, Simona Sacone, Silvia Siri

Freeway Traffic Modelling

Frontmatter
Chapter 3. First-Order Macroscopic Traffic Models
Abstract
Macroscopic traffic models describe the traffic behaviour at a high level of aggregation, i.e. the traffic dynamics is expressed through aggregate variables, such as traffic density, mean speed and flow. Macroscopic models rely on the analogy between the flow of vehicles and the flow of fluids or gases and are based on a limited number of equations that are relatively easy to handle. This chapter is devoted to describe a very relevant class of macroscopic models, i.e. first-order traffic flow models, which capture the dynamics of only one aggregate variable, namely, the traffic density. A very important first-order macroscopic model is the Lighthill–Whitham–Richards model, developed in the 50s, but still of interest nowadays both for theoretical analysis and practical applications. It is a continuous model, which describes the dynamics of the macroscopic variables through partial differential equations. The most famous discretised version of the Lighthill–Whitham–Richards model is the so-called Cell Transmission Model, developed in the 90s and very widespread in the communities of mathematicians and traffic engineers.
Antonella Ferrara, Simona Sacone, Silvia Siri
Chapter 4. Second-Order Macroscopic Traffic Models
Abstract
Second-order macroscopic traffic flow models introduce a second dynamic equation compared to first-order models, i.e. the equation describing the dynamics of the mean speed of vehicles. Second-order models were introduced in the 70s as continuous models, the earliest one being the so-called Payne–Whitham model. Some critiques arose on this class of models, focusing in particular on the dissimilarity between the flow of vehicles and the flow of molecules in fluids or gases. This criticism encouraged new developments of second-order models, leading to the model proposed by Aw and Rascle, and a similar model developed independently by Zhang. A discrete version of second-order models has been elaborated in the 90s, known as METANET. This discrete model, conceived both for freeway stretches and for networks, is very widespread in the engineering field and particularly suitable for prediction and control purposes.
Antonella Ferrara, Simona Sacone, Silvia Siri
Chapter 5. Microscopic and Mesoscopic Traffic Models
Abstract
Besides macroscopic traffic flow models, traffic modelling in freeway systems has also been treated with other general approaches, resulting in microscopic and mesoscopic models. Macroscopic models can surely represent large networks efficiently, since they adopt an aggregate representation of the traffic dynamics, but they generally lack the level of detail needed in modelling the individual drivers’ behaviours and choices. Microscopic models are, instead, conceived to explicitly reproduce the drivers’ responses to traffic patterns, reactions to traffic variations, interactions with other vehicles and route choices, i.e. most of the individual behaviours. Consequently, microscopic models are able to provide a lot of information about the features of traffic flow but they require a high computational effort, especially for large road networks. Mesoscopic models fill the gap between microscopic and macroscopic models, by representing the choices of individual drivers at a probabilistic level, but limiting the level of detail on driving behaviours.
Antonella Ferrara, Simona Sacone, Silvia Siri
Chapter 6. Emission Models for Freeway Traffic Systems
Abstract
It is widely recognised that road transport is one of the main sources of air pollution and that the measures to reduce pollution need to accurately take into account the contribution of road traffic systems. The definition of models for estimating chemical and thermal pollutants produced by vehicular traffic has been investigated by researchers for some decades. The existing models can be classified according to different aspects, such as the geographical scale, the model accuracy and the nature of the approach for computing emissions. However, in the wide range of existing models, only few are suitable for being integrated in management and control tool scheme for freeway traffic systems. These models must be simple enough to be adopted in online control applications but, at the same time, they have to provide a rather accurate estimation of pollutant emissions.
Antonella Ferrara, Simona Sacone, Silvia Siri
Chapter 7. State Estimation in Freeway Traffic Systems
Abstract
Freeway networks are generally equipped with different types of sensors which are able to measure traffic conditions in real time. Such sensors are placed in fixed positions on the road network and, hence, measure traffic variables in specific positions, often far from each other, because their number is limited by technological and financial issues. In addition, the measurements provided by traffic sensors can be noisy and affected by failures. On the other hand, for designing efficient traffic control and monitoring systems, it is required to know the values of the traffic variables (flow, density, speed) on the different road segments, in real time. For these reasons, the problem of traffic estimation is quite relevant and has attracted the attention of researchers in the past decades. Such a problem will have to face new challenges in the near future, due to the fast development of intelligent and connected vehicles, which are able to measure traffic states and to transmit them in real time. These new technologies will enable much more traffic information than in the past, but providing mobile data that are, by nature, disaggregated and asynchronous.
Antonella Ferrara, Simona Sacone, Silvia Siri

Freeway Traffic Control

Frontmatter
Chapter 8. An Overview of Traffic Control Schemes for Freeway Systems
Abstract
Some of the criticalities associated with traffic phenomena in freeway networks can be mitigated or even eliminated with suitable control strategies. The most important and evident drawback of traffic is surely congestion and, consequently, congestion reduction is one of the main objectives of traffic control policies. More recently, other control objectives have become relevant, including reduction of fuel consumptions and pollutant emissions, number of accidents, noise and so on. Researchers have investigated traffic control approaches for some decades and are still working on developing control schemes that, on the one hand, are more and more effective for improving the performance of the traffic system and, on the other hand, are easily implementable in real contexts.
Antonella Ferrara, Simona Sacone, Silvia Siri
Chapter 9. Implementation-Oriented Freeway Traffic Control Strategies
Abstract
When adopting optimisation-based control approaches in real time for freeway traffic systems, practical applicability and efficiency are extremely important aspects. The complexity of the traffic control problems to be solved increases with the dimension of the freeway system, making the centralised online application of the control strategies often problematic. In the literature, several solutions have been proposed in order to address these implementation issues. Some of them are aimed at simplifying the problem structure, while others are designed to reduce the overall computational and measurement transmission burden. This chapter focuses on different control solutions which are implementation-oriented. Specifically, distributed, decentralised and event-triggered control solutions for freeway traffic are discussed, also outlining the technological aspects which characterise their implementation.
Antonella Ferrara, Simona Sacone, Silvia Siri
Chapter 10. Control Strategies for Sustainable Mobility in Freeways
Abstract
Sustainability is nowadays a key issue for the development of strategies and policies in the context of mobility and transportation. In order to achieve a sustainable mobility system, by taking care of the needs of present and future generations, control strategies must take into account sustainability-related issues in an explicit manner. This means that the control methods developed nowadays must have the objectives not only of decreasing travel delays experienced by drivers in the traffic system but also of reducing emissions of pollutants, fuel consumptions, accidents, noise and so on. To this end, multi-class models and multi-class traffic control strategies are needed as well. If a multi-class model allows to capture the real dynamics of the traffic system in a more realistic way, multi-class traffic control strategies permit to regulate separately the flows of different vehicle classes, and this enables, for instance, the definition of particular policies for cars, different from those dedicated to trucks, according to specific plans defined by local authorities or traffic managers.
Antonella Ferrara, Simona Sacone, Silvia Siri
Chapter 11. Emerging Freeway Traffic Control Strategies
Abstract
Classical freeway traffic control approaches can be conveniently revisited in the light of the new technologies which have revolutionised data collection, data processing, communications and computing. In this chapter, the emerging freeway traffic control paradigms are illustrated, without claiming to be exhaustive, as the emerging control concepts are constantly evolving together with the new technologies on which they are based. The scenarios that unfold on the horizon are incredibly dense with potentialities and opportunities. Traffic data acquisition can be performed supplementing fixed sensors with probe vehicles. The overall traffic flow, even in case of mixed traffic consisting of conventional vehicles and intelligent vehicles, can be influenced by acting in a coordinated way at the level of the single intelligent vehicle. Large amounts of data can be collected, also exploiting unconventional data sources like social networks, making of paramount importance the development of traffic-oriented big data technologies, as well as efficient data mining techniques, in order to distinguish between useful and non-useful data and suitably process them. Privacy-preserving data sharing, cybersecurity, fault-tolerance and resilience concepts also play an important role in this new and challenging scenario.
Antonella Ferrara, Simona Sacone, Silvia Siri
Backmatter
Metadaten
Titel
Freeway Traffic Modelling and Control
verfasst von
Prof. Dr. Antonella Ferrara
Prof. Simona Sacone
Silvia Siri
Copyright-Jahr
2018
Electronic ISBN
978-3-319-75961-6
Print ISBN
978-3-319-75959-3
DOI
https://doi.org/10.1007/978-3-319-75961-6

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