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Rolling stock management
A train is made of a motive power system and passenger cars. One or several locomotives can contain the motive power system and pull or push passenger cars. Some trains with locomotives can be driven at both sides, those are push-pull trains. There can be a locomotive at each end of the train, or one locomotive and a cab in the passenger car at the opposite end. If a train is not push-pull, a turnaround usually requires to remove the locomotive at one end of the train and hang another locomotive at the other end. A train unit (also called multiple unit) gathers motive power system and passenger cars which cannot be uncoupled during operations. Train units can often be driven at both ends and can be coupled with other train units. Locomotives or train units can be powered by electricity or fuel (usually diesel).
In particular, electric trains can only move on an electried infrastructure with specic characteristics. European countries can have dierent electrication systems which are not compatible with all trains. For example, France has two electrication systems. Trains must also respect gauge or length restrictions depending of the network they run on. Trains that have same characteristics belong to a same rolling stock type. Train units that belong to dierent rolling stock types, can be coupled if their rolling stock types share some technical features: rolling stock types can be compatible. Once a train is acquired by a train operator, maintenance must be done. Maintenance makes rolling stock able to ensure service quality. Indeed, it prevents incidents and provides clean trains with comfort equipment (seat, light, air conditioner…) in good conditions. A great part of rolling stock maintenance is preventive: components are checked, repaired or replaced according to nominal wear indications rather than actual failure. Operations are done according to the total distance traveled or to specic temporal frequencies. In France, maintenance activities are structured into ve levels. The higher the level of maintenance, the heavier the tasks performed. Interventions are more frequent for low level maintenance. Level 1 maintenance is performed daily and does not need any specic facility. In level 1 maintenance, drivers or conductors check that safety devices work at the beginning of a day. Level 2 maintenance
contains operations performed in a shunting yard that has specic facilities. Level 2 maintenance is
made between two rail services that a train operates, so during o-peak hours or during the night. Level 2 maintenance contains light operations such as cleaning, technical checks of mechanical components, motorization and interior ttings. The frequency of most these operations varies from 4 times a week to once every 15 days. Level 3 maintenance gathers heavy maintenance operations. Such operations require immobilizing a train for several days for in-depth examinations. Level 3 maintenance is executed on a train every one or two years in a maintenance center. Level 4 and level 5 maintenance gather industrial maintenance operations. These operations are performed on a train every 10 years or more in industrial maintenance centers. Industrial maintenance contains complete overhaul or modernization operations.
Overview of passengers operations planning
Railway services are planed so that necessary resources which are infrastructure capacity, rolling stock and crews can be deployed. At a strategic level resources are sized. The decision horizon is often larger than ve years. Strategic decisions include the purchase of rolling stock and infrastructure building or upgrading. At tactical level, rail services are dened and resources are assigned. The decision horizon is between ve years and one day before operations. Tactical decisions include timetabling as well as rolling stock and crew assignment. At operational level, trac is managed in real-time. The decision horizon is often less than few hours. Operational decisions may change timetable or resource assignment to cope with disturbances.
In France, the timetable for a year is called the annual service. It is obtained thanks to tactical decisions which occur in four stages (SNCF Réseau [2018]) reported in Table 2.1. The rst stage is the preconstruction. Preconstruction decisions are made between ve years and one year before the annual service. The basic framework of the railway service is dened. During this stage a systematic timetable diagram for a 2 hour period and for a 24 hour period is made. Diagrams are obtained by dening rst systematic paths with stops. Such paths are called lines and dening lines is line planning. The frequency of lines is set in order to satisfy an expected demand. Then a periodic timetabling is made. During periodic timetabling, train paths of the lines are scheduled. The second stage is the construction and occurs between one year and six months before operations. During this stage train operating companies request train paths to the infrastructure manager. If a request is accepted, it is scheduled and appears in the annual service: timetabling is performed. At stations a platform track is assigned to each train path: this is platforming. Usually, the requests are
consistent with the timetable diagrams obtained in the preconstruction phase. Nevertheless, timetabling in construction phase is not periodic, for example holidays may change the passenger service. Once train paths are examined, train operating companies make a daytime rolling stock circulation plan. In a rolling stock circulation plan, a train is assigned to each train path.
Adaptation is the third stage of annual service planning. It takes place between six months and six days before operations. Train paths dened in the construction phase can be modied because of infrastructure works or special events. In adaptation phase, a complete rolling stock circulation is set. It consider maintenance as well as parking in nighttime or o-peak hours. In particular, shunting planning considers trains without passengers, which are parked or maintained in stations. A crew scheduling is also set.
The nal stage is the preoperational one and occurs between six days and few hours before operations. In this stage, last minute requests and planned or expected disturbances such as failures or strikes are considered. A nal timetable and resource assignment is set to be used by dispatchers. Railway planning is mostly resource centered. A planning problem deals with the use of specic resources. For example timetabling deals with the use of infrastructure capacity while rolling stock circulation concerns the use of rolling stock. Resources can be considered in a regional or national scale in which services are treated all along their path. Local scale planning details resource assignment or scheduling at major stations.
Many decision support tools or methods are used by infrastructure managers and train operating companies for service planning. Planners often use software tool which check the feasibility and precise the outcome of an assignment or a timetable. Software tools can go further and explore a set possible decisions to provide an optimal decision. Such tools integrate combinatorial optimization techniques. The interest for operation research in passenger railway planning has grown in the last decades: as train operating companies face competition in Europe, they aim to improve their performances. Moreover, infrastructure managers aim to optimize the use of capacity. Operations research have proposed relevant modeling approaches and algorithms to solve planning problems. In Section 2.2.2 we give some details about capacity use problems, and in Section 2.2.3 we focus on rolling stock. We refer the interested reader the literature (e.g., Caprara et al. [2007], Huisman et al. [2005] and Kroon et al. [2009]) for a deep review of operations research applications to European passengers rail services.
Rolling stock circulation planning
In rolling stock circulation planning, train operating companies need to cover all train paths with an
available number of trains. A train can be assigned to a trip if it respects technical characteristics such as gauge, electrication or length and its seats can carry the expected demand. In a eet made of train units, trains can be coupled or uncoupled during or between trips to adapt seat capacity. The train units coupled have to belong to identical or compatible rolling stock types. When a train nishes a trip at a station, its next trip can start either at the same station or at another one, then trains may run empty between these stations. The cost of rolling stock circulation integrates the distance traveled by trains. Rolling stock circulation contains maintenance, namely preventive maintenance that is operated depending on distance traveled or time frequency. Capacity of shunting yards used to park trains in daytime or nighttime is considered. In a eet made of train units, constraints due to position of train units in a train are also taken into account. When train units are coupled and uncoupled, the trip assignment must be consistent with the position of train units. For example, if a train made of two train units nishes a trip and gets uncoupled at a terminus station, which has dead end platform tracks, the original head train unit is at the bottom of the station. Therefore, after uncoupling, the head train unit has to leave the station last. The head train unit cannot be assigned to a train path that leaves the station before the train path assigned to the tail train unit. In the construction phase, a year before operations (Table 2.1), a daytime rolling stock circulation is made. Each day, trains are assigned to train paths. Nevertheless, the position of trains at the beginning and at the end of the day is not considered. In a complete rolling stock circulation, days are linked by including night time parking or maintenance. In France, eet managers dene maintenance tasks that have to be performed on trains. Light maintenance (level 2) can be performed on shunting yards of stations as well as in maintenance centers. Heavy maintenance (level 3) can only be performed in maintenance centers. Maintenance tasks are grouped into maintenance cycles. All the tasks of a maintenance cycle can be performed in few hours in case of light maintenance or several days in case of heavy maintenance. Fleet managers set maintenance cycles each time a train is parked at a shunting yard or a maintenance center. In the adaptation or preoperational phase, they must also change the rolling stock circulation when a train needs an extra maintenance because of an incident. This adaptation is the maintenance routing.
Table of contents :
1 Introduction
1.1 Context and motivation
1.2 Research objectives
1.3 Contributions
1.4 Outline of the thesis
2 Railway system and passenger transportation planning
2.1 Introduction to the railway system
2.1.1 Infrastructure capacity
2.1.2 Rolling stock management
2.2 Passengers railway operations planning
2.2.1 Overview of passengers operations planning
2.2.2 Train timetabling
2.2.3 Rolling stock circulation planning
2.3 Shunting and local scale planning
2.4 Conclusion
3 Overview of shunting problems modelling approaches
3.1 Shunting problems description
3.1.1 Shunting problems setup
3.1.2 Characteristics of shunting problems
3.1.3 Integrating shunting problems
3.2 Literature review
3.2.1 Classication of related works
3.2.2 Literature review on the Train Matching Problem
3.2.3 Literature review on the Shunting Maintenance Problem
3.2.4 Literature review on the Track Assignment Problem
3.2.5 Literature review on the Shunting Routing Problem
3.2.6 Shunting issues in rolling stock circulation problem
3.2.7 Other integrated problems in railway planning
3.3 Conclusion
4 MILP formulation for integrating maintenance and routing
4.1 Formal description of G-TUSP
4.1.1 Modelling principles
4.1.2 Trains
4.1.3 Infrastructure
4.1.4 Maintenance operations
4.1.5 Denition of the G-TUSP
4.2 MILP formulation
4.2.1 Basic formulation
4.2.2 Model strengthening
4.3 Instances generation and checking
4.3.1 Path generation
4.3.2 Alternative paths number reduction
4.3.3 Aggregated capacity feasibility check
4.4 Experiments
4.4.1 Instances description
4.4.2 Results
4.5 Conclusion
5 Sequential algorithms for the generalized train unit shunting problem
5.1 Sequential algorithms for G-TUSP
5.1.1 MILP formulation for TMP
5.1.2 MILP formulation for SMP and TMP
5.1.3 Heuristic for the TAP
5.2 Experimental analysis
5.2.1 Case study
5.2.2 Experimental results
5.3 Conclusion
6 Conclusion
6.1 Summary and conclusions
6.2 Future research .
