RAILWAY TRAFFIC RESCHEDULING APPROACHES TO MINIMISE DELAYS IN DISTURBED CONDITIONS by BO FAN A thesis submitted to The University of Birmingham for the degree of DOCTOR OF PHILOSOPHY School of Electronic, Electrical and Computer Engineering College of Engineering and Physical Sciences The University of Birmingham, UK August 2012 University of Birmingham Research Archive e-theses repository This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder. Abstract The advent of modern railway signalling and train control technology allows the implementation of advanced real-time railway management. Optimisation algorithms can be used to: minimise the cost of delays; find solutions that recover disturbed scenarios back to the operating timetable; improve railway traffic fluidity on high capacity lines; and improve headway regulation. A number of researchers throughout the world have previously considered the problem of minimising the cost of train delays and have used various optimisation algorithms for differing scenarios. However, little work has been carried out to evaluate and compare the different approaches. Firstly, the author of this thesis compares and contrasts a number of optimisation approaches that have been used previously and applies them to a series of common scenarios. The approaches considered are: brute force, first-come-first-served, Tabu search, simulated annealing, genetic algorithms, ant colony optimisation, dynamic programming and decision tree based elimination. It has been found that simple disturbances (i.e., one train delayed) can be managed efficiently using straightforward approaches, such as first-come-first-served. For more complex scenarios, advanced methods are found to be more appropriate. For the scenarios considered in this comparison, ant colony optimisation performed well: the delay cost is decreased by 30% compared with first-come-first-served. Secondly, in order to improve the currently available algorithm so that it can find more reliably optimal or close to optimal results within a practical computation time, a new hybrid algorithm, has been developed based on ant colony optimisation. In order to evaluate the new approach, 100 randomly generated delay scenarios were tested, and a comparison is made between the results of the new algorithm and first- come-first-served, brute force and standard ant colony optimisation. It is shown that the hybrid algorithm has an improved performance in terms of optimality and computation speed. Finally, a new multi-stage rescheduling approach for finding an optimal solution over multiple junctions is proposed. A case study is considered, and it is shown that the proposed approach performs well. Acknowledgements I am extremely grateful to my supervisor, Prof. Clive Roberts, for his continuous support, guidance, and patience. I have greatly benefited from his profound knowledge, plentiful experience, and insightful discussions. I much appreciate his encouragement and he provided me with many helpful suggestions and important advice during my research and academic writing. I would also like to extend my deep gratitude to Dr Paul Weston for his helpful suggestions, kind support and inspiration for this thesis and publications as well as the challenging research that lies behind it. Thanks also to the members of the Birmingham Centre for Railway Research and Education for supporting and helping daily research work. Let me also say thank you to Katherine Slater for proof reading my thesis. Finally, I would like to thank my parents and my wife. Without their love, support and encouragement, my study in the UK would not have been possible. Table of Contents ABSTRACT .......................................................................................................................................... 2 ACKNOWLEDGEMENTS ...................................................................................................................... 4 TABLE OF CONTENTS .......................................................................................................................... 5 LIST OF FIGURES ............................................................................................................................... 10 LIST OF TABLES ................................................................................................................................. 13 ABBREVIATIONS ............................................................................................................................... 15 CHAPTER 1: INTRODUCTION .............................................................................................................. 1 1.1 BACKGROUND .................................................................................................................................... 1 1.2 INTRODUCTION TO RAILWAY TRAFFIC MANAGEMENT ................................................................................ 3 1.2.1 Brief Introduction to Railway Timetabling ............................................................................. 3 1.2.2 Railway Signalling System ...................................................................................................... 3 1.2.3 Railway Train Control System ................................................................................................ 4 1.3 THE PURPOSE OF TRAIN CONTROL AND RESCHEDULING SYSTEMS ................................................................. 7 1.4 MOTIVATION AND RESEARCH OBJECTIVES ................................................................................................ 8 1.5 THESIS STRUCTURE ............................................................................................................................ 10 CHAPTER 2: REVIEW OF ALGORITHMS FOR RAILWAY RESCHEDULING AND THE DEVELOPMENT OF A BENCHMARK SCENARIO FOR ALGORITHM COMPARISON ................................................................ 11 2.1 HIGH LEVEL PARTITION OF RESCHEDULING OPTIMISATION ALGORITHMS ..................................................... 11 2.2 FUNDAMENTAL ALGORITHMS .............................................................................................................. 13 2.3 GRAPH-BASED ALGORITHMS ............................................................................................................... 16 2.3.1 Stage-to-Stage Transformations .......................................................................................... 16 2.3.2 Decision Trees ...................................................................................................................... 17 2.3.3 Alternative Graph Model...................................................................................................... 19 2.4 EVOLUTIONARY ALGORITHMS .............................................................................................................. 21 2.5 BENCHMARK SCENARIO TO THE SINGLE JUNCTION CASE STUDY .................................................................. 23 2.5.1 Junction and Benchmark ...................................................................................................... 24 2.5.2 Introduction to the Trains in this Case Study ....................................................................... 26 2.5.3 Introduction to the Simulator and Train Running Time Estimation ..................................... 27 2.5.4 Cost Functions ...................................................................................................................... 29 2.6 CONCLUSIONS .................................................................................................................................. 30 CHAPTER 3: SOLUTIONS OF THE BENCHMARK PROBLEM USING FUNDAMENTAL AND GRAPHICAL ALGORITHMS ................................................................................................................................... 32 3.1 BRUTE FORCE ................................................................................................................................... 32 3.1.1 Introduction to Brute Force Algorithm ................................................................................. 32 3.1.2 Study of Brute Force Algorithm in Railway Rescheduling .................................................... 33 3.1.3 Results and Summary ........................................................................................................... 35 3.2 FIRST-COME-FIRST-SERVED ................................................................................................................ 37 3.2.1 Introduction to the First-Come-First-Served Algorithm ........................................................ 37 3.2.2 Study of First-Come-First-Served in Railway Rescheduling .................................................. 37 3.2.3 Results and Summary ........................................................................................................... 38 3.3 DYNAMIC PROGRAMMING .................................................................................................................