Transportation Research Part E: Logistics and Transportation Review
An assessment of railway capacity
Introduction
One consequence of the globalization of the economy and the increasing integration of the international economies is a considerable growth in the entire transport sector. During the 1990s, many countries began to suffer from congestion in certain areas and on certain routes. Nowadays, there is no doubt about the congestion of the transport situation in some countries. The problem is now beginning to threaten economic competitiveness. Greater economic development cannot take place in the current transport scenario unless ambitious measures are taken. Revitalizing the railways is one of the principal measures proposed in European transport policy. The priority is to open up markets with the deregulation of the rail transport sector as one of the principal aims. The objective is to provide railway companies with access to the railway network on equal terms; this access will be determined by infrastructure managers. This has led many railroads to reevaluate their capacity. Capital expansion is a very costly means of increasing capacity. A more cost-effective solution is to manage the existing capacity more effectively using computer-based decision support systems.
Optimizing the use of railway infrastructure is a complex and difficult task. Therefore, numerous capacity studies must be performed in order to work out what part of extra traffic can be absorbed by the existing infrastructure and how much investment will be required for new infrastructure. The results of these studies must be rapid and precise in order to know how many route slots can be offered to railway operators and how much railway traffic can be supported by the current network. They must also provide regional and national authorities and the owners of the infrastructure with information that proves that investing in the development of the rail network is necessary and worthwhile financially.
Capacity, whose definition is a classical problem, has long been a significant issue in the railway industry. The goal of capacity analysis is to determine the maximum number of trains that would be able to operate on a given railway infrastructure, during a specific time interval, given the operational conditions. Numerous approaches and tools have been developed to address this problem; they are based on traffic patterns (Forsgren, 2003), single-track analytical models (Petersen, 1974), or algebraic approaches (Egmond, 1999). Several international companies are also working on similar computer-based systems:
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DEMIURGE (SNCF and Eurodecision, 2004) is a software program designed to assist in making rail network capacity studies. This software can evaluate a network’s capacity to absorb additional traffic, to locate bottlenecks, to assist in making decisions about infrastructure investments, to optimize current and future timetables, and to calculate the residual capacity of a timetable.
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CMS (AEA Technology Rail) provides a system to plan the effective utilization of the railway capacity. It offers an easy “what-if” scenario evaluation, automatic generation of timetables, simulation of operations to predict performance and identify remedies, identification of capacity available for sale, and usage forecasts based on improved timetables. However, CMS needs to be calibrated using updated punctuality data to ensure that its predictions are valid.
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RAILCAP (Stratec) measures how much of the available capacity is used by a given operation program in a straightforward way, and it offers a very detailed analysis of bottlenecks. However, it has one major disadvantage since the modelling requires a great deal of effort. RAILCAP requires detailed descriptions of the tracks, switches, crosses, signals and speed limits.
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VIRIATO (SMA and Partner) is mainly used for adapting infrastructure to future service concepts and coordinating several operators or products that share the same infrastructure. It allows the user to determine the amount of saturation of a specified line. It compresses a given timetable, and determines the saturation rate of a line or a part of a line as a percentage. This method leads to varying results for the same line, depending on the length of the section under consideration.
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CAPRES (Lucchini and Curchod, 2001) is a model for the elaboration and saturation of timetable variants. Through the use of iterations, this model determines all available extra trainpaths, given all the constraints and interconnections between lines. A disadvantage of this model is that the traditional network and operational data have to be completed with the information about where, when and how the network capacity must be used.
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FASTTRACK II (Multimodal Applied Systems) is a computer-based train dispatching and meet-pass model that is capable of producing a feasible train dispatching plan for a user-selected corridor, given a set of proposed train schedules and a corridor’s track configuration. It can be used to examine the feasibility of a set of proposed train schedules, test the impact of proposed changes in operating policies on train service, and measure both the theoretical and practical line capacity.
More information about these systems and other similar railway management systems can be found in (Barber et al., 2007).
Previous works have shown that several factors can affect capacity, and several methods have been proposed to assess it. However, since there is no commonly accepted measure of capacity, additional analytical analyses of these factors following recent recommendations of the Union of the European Railway Industries are needed. There is also a need for automatic tools that analyze different empirical methods.
In this paper, we review the main concepts and methods of assessing railway capacity, and we analyze the main factors that can affect it. In addition, we present a computer-based tool, the MOM system (Barber et al., 2006), which has been developed along the same lines as the above-mentioned tools. The MOM system is a highly functional tool that helps railway managers to provide efficient and reactive management of railway infrastructures. The MOM system can generate optimized railway schedules both off-line and on-line (when disruptions occur). It also provides information on railway network capacity and on timetable robustness, helping managers to make better decisions. In this work, we limit our study to the railway capacity module. This module provides several analytical and empirical methods that can be used to obtain conclusions about the capacity of railway networks and that support the process of adapting the railway infrastructure to traffic needs. The MOM system project has been developed according to the requirements of the Spanish Administration of Railway Infrastructure, ADIF.1
Section 2 presents the problem description: an introduction to railway capacity, types of capacity, and the factors that affect capacity. Section 3 presents a survey of methods to evaluate railway capacity. Section 4 presents our automated tool that is able to obtain conclusions about railway capacity. In Section 5, we perform several analytical and empirical capacity analyses on real networks. In Section 6, we analyze the effect of different parameters on railway capacity. Section 7 presents the new signaling and management system for the European Rail Network, and Section 8 presents our conclusions.
Section snippets
Problem description
An efficient utilization of the existing railway infrastructure is an essential component of a high-quality transportation system and has become a central task for railway infrastructure managers. The definition of standards and robust methods for its assessment are very important. Line capacity is, in essence, what the infrastructure managers have to sell as their final product.
Although capacity seems to be a self-explanatory term in common language, its scientific use may lead to substantial
Methods to evaluate railway capacity
Numerous approaches have been developed to evaluate railway capacity. The most relevant methods can be classified in three levels: Analytical Methods, Optimization Methods, and Simulation Methods.
A system for capacity analysis
The new policy of the European Union is to encourage open access to railway networks. This process has already begun in the Spanish Administration of Railway Infrastructure, ADIF, which is interested in using advanced computer tools to improve railway management. In collaboration with ADIF, the authors have developed a tool called MOM (acronym of the Spanish name: Modulo Optimizador de Mallas) that embeds analytical and optimization approaches in this context. This integrated system helps
Applying methods to evaluate railway capacity
In this section, we evaluate the performance of our tool with several real problems. We show some of its capabilities in real capacity studies.
How different parameters affect railway capacity
This example illustrates the influence of several factors that affect capacity.
The network selected for our example is the “Reinosa – Torrelavega” line. It has about 59 kilometers with nine stations and nine halts. The real network has a single track, but in this example, we will also simulate this line with a double track because it is the most common situation in many real railway lines. The chosen time window is 24 h. Currently, several types of trains run on this line. We choose two fast
Capacity analyses on the european rail traffic management system
The European Rail Traffic Management System (ERTMS)2 is the initiative from the European Commission to create a unique signaling standard as a cornerstone for the achievement of the interoperability of the trans-European rail network and is likely to be adopted by the rest of the world as well.
To account for the diversity of functional/operational requirements, three system levels of reference have been identified. There are already ERTMS commercial projects in several
Conclusions
In this paper, we have reviewed the term “capacity”, its different types, the methods to evaluate it, and the main parameters affecting it, as well as its importance in the railway sector.
Infrastructure authorities need software tools that help them better understand the economic trade-offs associated with trying to place ever more trains down an ever more congested rail asset. This includes lost ridership due to slower and less reliable schedules, operating cost increases particularly for
Acknowledgements
The authors are grateful to the anonymous referees for their helpful comments and valuable suggestions to improve the manuscript. We also appreciate the assistance of Jose Estrada of the Spanish Adminstration of Railway Infrastructure(ADIF). This work has been partially supported by the research projects TIN2004-06354-C02-01 (Min. de Educacion y Ciencia, Spain-FEDER), FOM-70022/T05 (Min. de Fomento, Spain), GV/2007/274 (Generalidad Valenciana) and by the Future and Emerging Technologies Unit of
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