tuclogo.gif (9701 bytes) ΠΟΛΥΤΕΧΝΕΙΟ ΚΡΗΤΗΣ
 Εργαστήριο Δυναμικών Συστημάτων και Προσομοίωσης

Technical University Of Crete
Department Of Production Engineering
And Management

  

Integrated Control Of Traffic Flow
In Corridor Networks

  

Thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy

 by
Christina Diakaki


Chania, Greece, December 1999

Abstract

Traffic congestion in corridor networks is notoriously increasing. The resulting negative impacts include significant delays and the associated environmental problems. According to field and simulation investigations, a significant amelioration of traffic conditions may be achieved as a result of the appropriate integration of various control measures such as ramp metering, route guidance, and signal control. It is the scope of this thesis is to develop a systematic, simple, and generic methodology for the integration of the previously mentioned control measures.

The proposed IN-TUC strategy addresses in an integrated way the problem of corridor network control with the goal of producing traffic-responsive settings for the various control elements included in a corridor network. IN-TUC consists of three distinct interacting parts, the urban traffic control part, the ramp metering part, and the route guidance part. For urban traffic control, a novel strategy, TUC, has been developed. Control objective of TUC is the homogeneous utilisation of the capacity of the controlled urban network. This control objective is approached through the appropriate manipulation of the green splits at urban signalised junctions. For ramp metering, the ALINEA strategy is used. The aim of ALINEA is to regulate the traffic flow entering the motorway so as to maintain the mainstream occupancy at a desired pre-specified level. This way, ALINEA manages to reduce congestion and increase the motorway throughput. Finally, for route guidance, availability of variable message signs is assumed that provide suggestions to the drivers on the routes to follow so as to minimise their individual travel times. For this part of the strategy, a simple control law is applied based on the concept of equalising the travel times between two alternative routes, which leads to user-optimal conditions.

The three aforementioned parts of IN-TUC strategy are integrated in the sense of the mutual exchange of measurements and decisions. This approach allows for the independent use of the integrated control applications, and the easy extensibility and expandability of the control system. Moreover, the approach ensures the functionality of the system in case of failure or pause of any of the integrated control applications. IN-TUC is built upon well-known methods of the Automatic Control Theory. This has led to robustness with respect to measurement inaccuracies so that even in case of insufficient or incorrect data the strategy reacts correctly to the prevailing traffic conditions; simplicity and transparency of the real-time code and of the design procedure; and generality so that the strategy may be transferred with minor modifications to networks with arbitrary topology and characteristics.

Extensive simulation tests of the integrated strategy and its parts indicated high efficiency, which was also demonstrated during the field-implementation and evaluation of IN-TUC application to a part of the Glasgow M8 corridor network in Scotland, where IN-TUC has been operational since February 1998.

Table of Contents

Acknowledgements
Curriculum Vitae
Abstract
Notation

1. Introduction

2. Introduction to the Traffic Control of Road Networks

2.1 Road Traffic Control
2.2 Urban Road Network Control

2.2.1 Introduction
2.2.2 Classification of Control Strategies
2.2.3 Co-ordinated Traffic-Responsive Control Strategies

2.3 Motorway Network Control

2.3.1 Introduction
2.3.2 Ramp Metering Strategies

2.4 Route Guidance and Driver Information Systems

2.4.1 Introduction
2.4.2 Route Guidance Strategies

2.5 Integrated Corridor Network Control

2.5.1 Introduction
2.5.2 Problems and Progress

2.6 Introduction to the Proposed Methodology

2.6.1 The Integrated Strategy
2.6.2 The Urban Traffic Control Strategy

3. Road Traffic Modelling

3.1 Introduction

3.2 The Control Design Model

3.2.1 Introduction to the Store-and-Forward Modelling Approach
3.2.2 Model Development

3.3 The Simulation Model

3.3.1 Introduction
3.3.2 The METACOR Modelling Tool
3.3.3 Control Consideration
3.3.4 Performance Criteria

4. The IN-TUC Strategy

4.1 Introduction
4.2 Structure of the Integrated Strategy
4.3 Urban Traffic Control

4.3.1 Introduction
4.3.2 Regulator Design
4.3.3 Alternative Multivariable Regulators
4.3.4 The Gating Feature of the Multivariable Regulators
4.3.5 Enhancement of the Gating Feature
4.3.6 Application of Constraints

4.4 Ramp Metering
4.5 Route Guidance
4.6 Real-Time Measurements

4.6.1 Introduction
4.6.2 Replacement of Missing Data
4.6.3 Estimation of Numbers of Vehicles within Links

5. Application to an Example Network

5.1 Introduction
5.2 Application of IN-TUC to the Example Network

5.2.1 Modelling the Example Network for the Application of IN-TUC
5.2.2 Application of TUC to the Example Network
5.2.3 Application of ALINEA to the Example Network
5.2.4 Application of the Route Guidance Strategy to the Example Network

5.3 Application of METACOR to the Example Network
5.4 Design Investigations of IN-TUC

5.4.1 Selection of Parameters for the TUC Strategy

5.4.1.1 Selection of Weighting Matrices
5.4.1.2 Selection of Control Matrices
5.4.1.3 Sensitivity Investigations of Selected Control Matrices
5.4.1.4 Selection of Parameter b for the Enhancement of the Gating Feature of TUC

5.4.2 Selection of Parameters for the Route Guidance Strategy
5.4.3 Impact of the Estimation Parameters

6. Simulation Investigations

6.1 Introduction
6.2 Investigation of TUC Strategy

6.2.1 Introduction
6.2.2 Investigations with Direct x-Measurements

6.2.2.1 Investigations in Various Traffic Conditions
6.2.2.2 Investigations in Incident Cases

6.2.3 Investigations with Estimations Instead of Direct x-Measurements

6.2.3.1 Impact of Detector Locations
6.2.3.2 Investigations in Various Traffic Conditions and Incident Cases

6.2.4 Conclusions

6.3 Investigation of IN-TUC Strategy

6.3.1 Introduction
6.3.2 Investigations with Direct x-Measurements

6.3.2.1 Investigations in Various Traffic Conditions
6.3.2.2 Investigations in Incident Cases

6.3.3 Investigations with Estimations Instead of Direct x-Measurements
6.3.4 Conclusions

7. Real-life Implementation and Evaluation of the IN-TUC Strategy

7.1 Introduction
7.2 Description of the Glasgow M8 Corridor Network
7.3 Application of IN-TUC to the Glasgow M8 Corridor Network

7.3.1 The Control Model of the Glasgow M8 Corridor Network
7.3.2 Specific Application Issues
7.3.3 Specific Application Constraints

7.4 Evaluation of the IN-TUC Strategy

7.4.1 Methodology
7.4.2 Technical Assessment
7.4.3 Users’ Acceptance Assessment
7.4.4 Impact Assessment
7.4.5 Safety Evaluation
7.4.6 Concluding Remarks

8. Conclusions and Future Work

References

Appendices

A Linear-Quadratic Optimal Control

A.1 Problem Formulation
A.2 Linear-Quadratic (LQ) Methodology
A.3 Linear-Quadratic-Integral (LQI) Methodology

B Determination of Weighting Matrix Q

C Optimality of Algorithm

C.1 General
C.2 Solution of the Optimisation Problem
C.3 Proof of Algorithm Optimality

D Estimation of Number of Vehicles within Links

E LQI Problem and Control Matrices