Reliability and heterogeneity of railway services

Reliability is one of the key factors in transportation, both for passengers and for cargo. This paper examines reliability in public railway systems. Reliability of railway services is a complex matter, since there are many causes for disruptions and at least as many causes for delays to spread around in space and time. One way to increase the reliability is to reduce the propagation of delays due to the interdependencies between trains. In this paper we attempt to decrease these interdependencies by reducing the running time differences per track section, i.e. by creating more homogeneous timetables. Because of the complexity of railway systems, we use network wide simulation for the analysis of the alternative timetables. We report on both theoretical and practical cases. Besides a comparison of different timetables, also general timetabling principles are deduced.heterogeneity;simulation;reliability;transportation;railways

Operations research in passenger railway transportation

In this paper, we give an overview of state-of-the-art OperationsResearch models and techniques used in passenger railwaytransportation. For each planning phase (strategic, tactical andoperational), we describe the planning problems arising there anddiscuss some models and algorithms to solve them. We do not onlyconsider classical, well-known topics such as timetabling, rollingstock scheduling and crew scheduling, but we also discuss somerecently developed topics as shunting and reliability oftimetables.Finally, we focus on several practical aspects for each of theseproblems at the largest Dutch railway operator, NS Reizigers.passenger railway transportation;operation research;planning problems

Reliability of Railway Systems

Openbaar vervoer speelt een belangrijke rol in de mobiliteit in Nederland en andere landen. Om het treinverkeer concurrerend te houden met de auto, is een goede prijs-kwaliteitverhouding vereist. Één van de belangrijkste kwaliteitsmaatstaven is het op tijd rijden van de treinen. Vertragingen hebben veel verschillende oorzaken. Bovendien verspreiden opgelopen vertragingen zich zowel in plaats als tijd door het spoornetwerk. De maatschappelijke, bedrijfsmatige en wetenschappelijke relevantie van onderzoek naar het op tijd rijden van treinen is overduidelijk. Het proefschrift verschaft een duidelijk overzicht van de eigenschappen van een spoorsysteem met betrekking tot betrouwbaarheid. Verder worden enkele modellen ontwikkeld die kunnen helpen bij het opstellen van betrouwbare dienstregelingen. Een spoorwegsysteem kan worden gezien als een heel groot en complex stochastisch dynamisch systeem. “Betrouwbaarheid van Spoorwegsystemen” beschrijft wiskundige modellen voor de evaluatie en optimalisatie van spoorwegdienstregelingen. Speciale aandacht is er voor de verdeling van rijtijdspeling. Deze spelingen kunnen erg nuttig zijn in het beperken van vertragingsoverdracht. De effectiviteit van deze spelingen is echter erg afhankelijk van de locatie binnen de treinrit. Een verassende, maar potentieel effectieve regel voor de spelingsverdeling is ontwikkeld om de verspreiding van vertragingen te verminderen. Een ander belangrijk onderwerp is de heterogeniteit van het treinverkeer, of, in andere woorden, de snelheidsverschillen tussen de treinen. Naast het feit dat wordt aangetoond dat er een sterke correlatie is tussen snelheidsverschillen en betrouwbaarheid, zijn er nieuwe maten ontwikkeld die de mate van heterogeniteit van het treinverkeer aangeven. Verder wordt een innovatief stochastisch lineair programmeringsmodel gepresenteerd dat niet alleen in staat is om dienstregelingen te evalueren, maar ook te optimaliseren. Het model integreert de meeste spoorwegafhankelijkheden en minimaliseert de gemiddelde aankomstvertraging rechtstreeks. Het model laat zien dat aanzienlijke verbeteringen mogelijk zijn in vergelijking met de huidige dienstregeling in Nederland. Verschillende varianten van het model zijn beschreven die voor een breed scala aan problemen ingezet kan worden.Public transport plays a key role in mobility in the Netherlands and other countries. It has been recognized that the on-time performance is one of the key performance indicators in public transport. Many different internal and external factors cause the train operations to be disturbed. Moreover, incurred delays are often propagated to other trains and to other parts of the network. The societal, managerial, and scientific relevance of research on the on-time performance of railway systems are eminent. This thesis provides a clear picture of the reliability of railway systems. A railway system can be considered as a very large and complex stochastic dynamic system. “Reliability of Railway Systems” describes mathematical models for the evaluation and optimization of railway timetables. Special attention is given to the allocation of running time supplements. These supplements can be very useful in containing delay propagation. However, the effectiveness of these supplements highly depends on the location within the train line. A surprising, but potentially effective supplement allocation rule is developed to decrease the propagation of delays. Another important subject is the heterogeneity of train traffic, or in other words the speed differences. Besides showing a strong correlation between speed differences and reliability, new measures were developed to capture the heterogeneity. Furthermore, an innovative stochastic linear program is presented that is not only able to evaluate, but also to optimize timetables. It integrates most railway dependencie

Stochastic Improvement of Cyclic Railway Timetables

Real-time railway operations are subject to stochastic disturbances. However, a railway timetable is a deterministic plan. Thus a timetable should be designed in such a way that it can cope with the stochastic disturbances as well as possible. For that purpose, a timetable usually contains time supplements in several process times and buffer times between pairs of consecutive trains. This paper describes a Stochastic Optimization Model that can be used to allocate the time supplements and the buffer times in a given timetable in such a way that the timetable becomes maximally robust against stochastic disturbances. The Stochastic Optimization Model was tested on several instances of NS Reizigers, the main operator of passenger trains in the Netherlands. Moreover, a timetable that was computed by the model was operated in practice in a timetable experiment on the so-called “Zaanlijnâ€. The results show that the average delays of trains can often be reduced significantly by applying relatively small modifications to a given timetable.Railway Timetabling;Stochastic Optimization;Robustness

Reliability and heterogeneity of railway services

Reliability is one of the key factors in transportation, both for passengers and for cargo. This paper examines reliability in public railway systems. Reliability of railway services is a complex matter, since there are many causes for disruptions and at least as many causes for delays to spread around in space and time. One way to increase the reliability is to reduce the propagation of delays due to the interdependencies between trains. In this paper we attempt to decrease these interdependencies by reducing the running time differences per track section, i.e. by creating more homogeneous timetables. Because of the complexity of railway systems, we use network wide simulation for the analysis of the alternative timetables. We report on both theoretical and practical cases. Besides a comparison of different timetables, also general timetabling principles are deduced.Reliability is one of the key factors in transportation, both for passengers and for cargo. This paper examines reliability in public railway systems. Reliability of railway services is a complex matter, since there are many causes for disrup

Cyclic Railway Timetabling: a Stochastic Optimization Approach

Real-time railway operations are subject to stochastic disturbances. However, a railway timetable is a deterministic plan. Thus a timetable should be designed in such a way that it can absorb the stochastic disturbances as well as possible. To that end, a timetable contains buffer times between trains and supplements in running times and dwell times. This paper first describes a stochastic optimization model that can be used to find an optimal allocation of the running time supplements of a single train on a number of consecutive trips along the same line. The aim of this model is to minimize the average delay of the train. The model is then extended such that it can be used to improve a given cyclic timetable for a number of trains on a common infrastructure. Computational results show that the average delay of the trains can be reduced substantially by applying relatively small modifications to the timetable. In particular, allocating the running time supplements in a different way than what is usual in practice can be useful

Reinventing Crew Scheduling at Netherlands Railways

In this paper we describe the successful application of a sophisticated Operations Research model and the corresponding solution techniques for scheduling the 6,500+ drivers and conductors of the Dutch railway operator NS Reizigers (Netherlands Railways). In 2001 the drivers and conductors were very dissatisfied with the structure of their duties, which led to nation wide strikes. However, the application of the model described in this paper led to the development of an alternative production model (‘Sharing Sweet & Sour’) that both satisfied the drivers and conductors, and at the same time supported an increment of the punctuality and efficiency of the railway services. The plans produced according to the alternative production model trimmed personnel costs by about $4.8million (or1.2$7 million per year are also achievable

Stochastic Improvement of Cyclic Railway Timetables

Real-time railway operations are subject to stochastic disturbances. However, a railway timetable is a deterministic plan. Thus a timetable should be designed in such a way that it can cope with the stochastic disturbances as well as possible. For that purpose, a timetable usually contains time supplements in several process times and buffer times between pairs of consecutive trains. This paper describes a Stochastic Optimization Model that can be used to allocate the time supplements and the buffer times in a given timetable in such a way that the timetable becomes maximally robust against stochastic disturbances. The Stochastic Optimization Model was tested on several instances of NS Reizigers, the main operator of passenger trains in the Netherlands. Moreover, a timetable that was computed by the model was operated in practice in a timetable experiment on the so-called “Zaanlijn”. The results show that the average delays of trains can often be reduced significantly by applying relatively small modifications to a given timetable

Cyclic Railway Timetabling: a Stochastic Optimization Approach

Real-time railway operations are subject to stochastic disturbances. However, a railway timetable is a deterministic plan. Thus a timetable should be designed in such a way that it can absorb the stochastic disturbances as well as possible. To that end, a timetable contains buffer times between trains and supplements in running times and dwell times. This paper first describes a stochastic optimization model that can be used to find an optimal allocation of the running time supplements of a single train on a number of consecutive trips along the same line. The aim of this model is to minimize the average delay of the train. The model is then extended such that it can be used to improve a given cyclic timetable for a number of trains on a common infrastructure. Computational results show that the average delay of the trains can be reduced substantially by applying relatively small modifications to the timetable. In particular, allocating the running time supplements in a different way than what is usual in practice can be useful.railway transportation;stochastic optimization;punctuality;buffer times;cyclic timetables

Operations Research in Passenger Railway Transportation

In this paper, we give an overview of state-of-the-art OperationsResearch models and techniques used in passenger railway transportation. For each planning phase (strategic, tactical and operational), we describe the planning problems arising there and discuss some models and algorithms to solve them. We do not only consider classical,well-known topics such as timetabling, rolling stock scheduling and crew scheduling, but we also discuss some recently developed topics as shunting and reliability of timetables.Finally, we focus on several practical aspects for each of theseproblems at the largest Dutch railway operator, NS Reizigers.operations research;planning;passenger railway transportation