Personalized Crew Rostering at Netherlands Railways
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Personalized Crew Rostering at Netherlands Railways Geert de Pont University of Tilburg Preface Before you lies the thesis Personalized Crew Rostering at Netherlands Railways. The research and the writing were done during a 7-month internship at Nether- lands Railways, division NS reizigers, department of logistics, in order to finalize my studies Econometrics and Operations Research at the University of Tilburg. Here I want to express my gratitude to my family and friends who helped me finishing my studies. In particular, my parents. Without their continuous support I would not have been in the position where I am right now. Furthermore, I would like to thank a number of people, who helped me finishing this thesis. First of all, I would like to thank my supervisors at NS, Dennis Huisman and Erwin Abbink for giving me the opportunity to conduct this research. Their knowledge, assistance and advice during my internship have been of great value to me. Special thanks goes out to my supervisor at the University of Tilburg, Willem Haemers, as well. Furthermore, I would like to thank my colleagues at NS – Roger Haenen, Pieter-Jan Fioole and Martijn van Beek – for creating a pleasant atmosphere for me to work in. Finally, I would like to thank G´abor Mar´oti for teaching me the basics of LATEX. I have worked with great pleasure and interest at this assignment. It has given me great insight in the practical side of Operations Research, especially in the field of linear programming problems. The expertise at NS and the quality of the available software were very high and I am thankful that they were available to me. Geert de Pont November 29, 2006 iii iv Abstract For each driver and conductor of a passenger railway operator a roster needs to be constructed, specifying which tasks he/she has to execute each day. Constructing rosters for such large transport organizations is a very complex problem. Therefore, the roster process at many railway operators is simplified by con- structing non-personalized rosters. As a result, personal prefer- ences on working hours cannot be taken into account. In this thesis, the crew rostering problem is discussed, in par- ticular at the main Dutch passenger railway operator, Nether- lands Railways. A method to construct personalized rosters is explained in detail. This method constructs rosters by split- ting the roster process in two phases. The performance of the method is tested on real-life instances of Netherlands Railways. v vi Contents Abstract v 1 Introduction 1 2 Netherlands Railways 3 3 Problem definition 7 3.1 CrewSchedulingandCrewRosteringatNS . 7 3.1.1 Creatingduties ........................ 7 3.1.2 Constructingtherosters . 8 3.2 Analysisofthecurrentrostermethod . 9 3.3 Personalrosters............................ 10 3.4 Objectivesoftheresearch . 10 4 Review on literature of crew rostering 11 4.1 Twoapproaches............................ 11 4.2 Personalizedrostering . 12 5 A method to construct rosters for NS 15 5.1 Twophases .............................. 15 5.2 Solutionapproach .......................... 16 6 First phase 17 6.1 Enumerationprocess . 17 6.1.1 Enumerationprocess. 18 6.1.2 Legalityconditions . 19 6.2 Selectingtherosters . .. .. .. .. .. .. .. .. .. .. 21 6.2.1 Thesetpartitioningproblem . 21 6.2.2 Thecostfunction. .. .. .. .. .. .. .. .. .. 22 6.3 Reducing the combinatorial size of the problem . .. 23 7 Second phase 25 7.1 Notation................................ 25 7.2 Decisionvariables.. .. .. .. .. .. .. .. .. .. .. 26 7.3 Constraints .............................. 26 7.3.1 Assignmentconstraints . 26 7.3.2 Constraints due to the CAO and ATW . 27 7.3.3 “Overtime”distribution . 35 7.3.4 “SweetandSour”distribution . 35 vii viii CONTENTS 7.4 Theobjectivefunction . 36 7.4.1 Objectivefunctions. 37 8 Implementation issues 39 8.1 Firstphase .............................. 39 8.2 Secondphase ............................. 40 9 Data and cases 41 9.1 Data.................................. 41 9.2 Cases ................................. 41 9.2.1 Preferences .......................... 42 9.2.2 Cyclic pattern rosters and adjusted preferences . .. 44 10 Computational results 47 10.1Firstphase .............................. 47 10.1.1 Parametersetting . 47 10.1.2 Results ............................ 48 10.2Secondphase ............................. 49 10.2.1 Parametersettings . 49 10.2.2 Results ............................ 49 11 Conclusions and recommendations 55 11.1Conclusions .............................. 55 11.2 Recommendations and further research. 56 A Lists of definitions and rules 59 A.1 Duties ................................. 59 A.2 Legalityrules ............................. 60 A.2.1 The Collective Labour Agreement of NS (CAO). 60 A.2.2 The Dutch working hours act (ATW) . 61 A.2.3 “SharingSweet&Sour”rules . 61 Chapter 1 Introduction Netherlands Railways (NS) is the major Dutch passenger railway operator. Every day around five thousand passenger trips are carried out by NS around their railway network. The trains used for the transport are staffed with con- ductors and drivers. There are currently around seven thousand drivers and conductors working at NS. For every driver and conductor a roster needs to be created that indicates at what times which tasks he/she has to do. Conductors and drivers are called crew members in the literature on rail crew rostering. In the remainder of this chapter, we refer to drivers and/or conductors if we use the words crew members. The drivers and conductors are working at crew bases. The tasks for the crew members are allocated to the crew bases and combined till complete units of work are generated. This process is called crew scheduling. The allocation of the complete units of work to the crew members is called crew rostering. The largest crew base of NS is Utrecht, where around 300 drivers and 400 conductors work. Rostering all the crew members of a crew base is a complex problem. NS reduces the complexity of the problem by dividing the group of crew members into smaller subgroups. Each subgroup gets assigned a part of the amount of work. Instead of creating a personal roster for every crew member in that subgroup, one roster is created for the subgroup. Since the roster is used by all crew members in the subgroup, personal preferences on working hours cannot be taken into account. A more detailed description of the crew planning process is described in Chapter 3. Over the years there has been a lot of progress in the field of crew rostering. Commercial crew rostering systems have been implemented successfully at some major airlines. With the help of these systems, personal rosters can be created. NS is interested in implementing a commercial crew rostering system to create personal rosters. This thesis reports on an method to create personal rosters. The method is tested on drivers working at crew base Utrecht. This test will give more insight into personalized rostering and its applicability at NS is attained. Before giving a detailed description of the method, Chapter 2 provides us with a brief overview of the company structure of the NS. Next, the current crew planning process is discussed in Chapter 3. Chapter 4 gives an overview of the literature on crew rostering. The method to create rosters is introduced in Chapter 5. This method splits the roster process in two phases. The first phase is explained in Chapter 6, the second in Chapter 7. Chapter 8 discusses 1 2 CHAPTER 1. INTRODUCTION the implementation issues of the method. The used data and the cases that are tested are described in Chapter 9. The results of the tests are presented in Chapter 10, followed by some concluding remarks in Chapter 11. Chapter 2 Netherlands Railways The NS as we know it today did not exist up till 1937. Before that time, a couple of small companies controlled the railway network. Then, in 1937, a company was established that was fully responsible for all the train services in the country. This company is known as Nederlandse Spoorwegen (NS) and is still operative today. Until 1995, the Dutch government was complete owner of the company. Thereafter, it retreated as owner and the NS became an independent company with the government as sole stockholder. NS provides the passenger transport over the most heavily used railway network of the world. It is the ambition of the NS to be one of Europe’s best passenger railway operators with reliable passenger transport and high customer satisfaction. The current mission statement of NS is therefore formulated as: “Providing safe, comfortable and non-delayed transportation of pas- sengers through attractive stations.” After the privatizing there was a massive restructuring of the organization in 2001. From this time on, NS split the company in several sections, namely Passenger Transport, Hub Development and Construction. An overview of the current structure of the company is visualized in Figure 2.1. The sections are split in subsections, each with its own tasks and responsibilities. For exam- ple, NS Stations has full responsibility for all the station buildings. NS Com- merce makes sure the products and services are customer directed. From all subsections NS Reizigers (NSR), having 10,000 employees and over 1,000,000 customers, is the largest subsection. They are responsible for the domestic pas- senger transport. Furthermore, they try to provide a robust timetable for the trains and spread reliable information during disruptions. Moreover, they try to provide their customers with sufficient and comfortable rolling stock. To summarize, NSR has full responsibility for all the issues concerning passenger railway transport. An overview of the structure of NSR is depicted in Figure 2.2. As can be seen from the chart, NSR is divided into a couple of departments and four networks. These networks are Randstad South, Randstad North, North East and South. Each network has its own center for adjusting the train network 3 4 CHAPTER 2. NETHERLANDS RAILWAYS Executive Board Support Companies Company Units and Subsidiaries Passenger Transport Hub Development Construction NS Passengers NS Commerce NS Stations Strukton NS International NS Real Estate NedRailways NedTrain Figure 2.1: Organization chart of NS for the specific network.