| 1. |
- Andersson, Emma, 1983-, et al.
(författare)
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Improved Railway Timetable Robustness for Reduced Traffic Delays – a MILP approach
- 2015
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Ingår i: 6th International Conference on Railway Operations Modelling and Analysis, Tokyo, Mars 23-26, 2015..
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Konferensbidrag (refereegranskat)abstract
- Maintaining high on-time performance and at the same time having high capacity utilization is a challenge for several railway traffic systems. The system becomes sensitive to disturbances and delays are easily propagating in the network. One way to handle this problem is to create more robust timetables; timetables that can absorb delays and prevent them from propagating. This paper presents an optimization approach to reduce the propagating of delays with a more efficient margin allocation in the timetable. A Mixed Integer Linear Programming (MILP) model is proposed in which the existing margin time is re-allocated to increase the robustness for an existing timetable. The model re-allocates both runtime margin time and headway margin time to increase the robustness at specific delay sensitive points in a timetable. We illustrate the model’s applicability for a real-world case where an initial, feasible timetable is modified to create new timetables with increased robustness. These new timetables are then evaluated and compared to the initial timetable. We evaluate how the MILP approach affects the initial timetable structure and its capability to handle disturbances by exposing the initial and the modified timetables to some minor initial disturbances of the range 1 up to 7 minutes. The results show that it is possible to reduce the delays by re-allocating margin time, for example, the total delay at end station decreases with 28 % in our real-world example.
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| 2. |
- Andersson, Emma, 1983-, et al.
(författare)
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Introducing a New Quantitative Measure of Railway Timetable Robustness Based on Critical Points
- 2013
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Ingår i: 5th International Seminar on Railway Operations Modelling and Analysis - RailCopenhagen 2013. - 9788773272466
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Konferensbidrag (refereegranskat)abstract
- The growing demand for railway capacity has led to high capacity consumption at times and a delay-sensitive network with insufficient robustness. The fundamental challenge is therefore to decide how to increase the robustness. To do so there is a need for accurate measures that return whether the timetable is robust or not and indicate where improvements should be made. Previously presented measures are useful when comparing different timetable candidates with respect to robustness, but less useful to decide where and how robustness should be inserted. In this paper, we focus on points where trains enter a line, or where trains are being overtaken, since we have observed that these points are critical for the robustness. The concept of critical points can be used in the practical timetabling process to identify weaknesses in a timetable and to provide suggestions for improvements. In order to quantitatively assess how crucial a critical point may be, we have defined the measure RCP (Robustness in Critical Points). A high RCP value is preferred, and it reflects a situation at which train dispatchers will have higher prospects of handling a conflict effectively. The number of critical points, the location pattern and the RCP values constitute an absolute value for the robustness of a certain train slot, as well as of a complete timetable. The concept of critical points and RCP can be seen as a contribution to the already defined robustness measures which combined can be used as guidelines for timetable constructors.
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| 3. |
- Andersson, Emma, et al.
(författare)
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Robustness in Swedish Railway Traffic Timetables
- 2011
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Ingår i: Railrome 2011.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A tendency seen for quite some time in the Swedish railway network is a growing demand for capacity which no longer can be accommodated. This causes congestion and delays, and the relationships between the trains and how they affect eachother are significantly harder to overview and analyse. Railway traffic timetables normally contain margins to make them robust, and enable trains to recover from certain delays. How effective these margins are, depends on their size and location as well as the frequency and magnitude of the disturbances that occur. Hence, it is important to include marigns so, that they can be used operationally to recover from a variety of disturbances and not restricted to a specific part of the line and/or the timetable. In a case study we compare the performance of a selection of passenger train services to the different prerequisites given by the timetable (e.g. available margins and their location, critical train dependencies). The study focuses on the Swedish Southern mainline between Stockholm and Malmö on which a wide variety of train services operate, e.g. freight trains, local and regional commuter train services as well as long-distance trains with different speed profiles. The analysis shows a clear mismatch between where margins are placed and where delays occur. We also believe that the most widely used performance measure, which is related to the delay when arriving at the final destination, might give rise to an unnecessarily high delay rate at intermediate stations.
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| 4. |
- Andersson, Emma V.
(författare)
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Assessment of Robustness in Railway Traffic Timetables
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A tendency seen for the last decades in many European railway networks is a growing demand for capacity. An increased number of operating trains has led to a delay sensitive system where it is hard to recover from delays, where even relatively small delays are easily propagating to other traffic.The overall aim of this thesis is to analyse the robustness of railway traffic timetables; why delays are propagating in the network and how the timetable design and dispatching strategies influence the delays. In this context we want to establish quantitative measures of timetable robustness. There is a need for measures that can be used by the timetable constructors. Measures that identify where and how to improve the robustness and thereby indicating how and where margin time should be inserted. It is also important that the measures can capture interdependencies between different trains.In this thesis we introduce the concept of critical points, which is a practical approach to identify robustness weaknesses in a timetable. In contrast to other measures, critical points can be used to identify specific locations in both time and space. The corresponding measure, Robustness in Critical Points (RCP) provides the timetable constructors with concrete suggestions for which trains that should be given more runtime or headway margin. The measure also identifies where the margin time should be allocated to achieve a higher robustness.In a case study we show that the delay propagation is highly related to the operational train dispatching. This study shows that the current prioritisation rule used in Sweden results in an economic inefficiency and therefore should be revised. This statement is further supported by RCP and the importance of giving the train dispatchers more flexibility to efficiently solve conflict situations.
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| 5. |
- Andersson, Emma V., 1983-, et al.
(författare)
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Quantifying railway timetable robustness in critical points
- 2013
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Ingår i: Journal of Rail Transport Planning and Management. - : Elsevier. - 2210-9706 .- 2210-9714. ; 3:3, s. 95-110
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Tidskriftsartikel (refereegranskat)abstract
- Several European railway traffic networks experience high capacity consumption during large parts of the day resulting in delay-sensitive traffic system with insufficient robustness. One fundamental challenge is therefore to assess the robustness and find strategies to decrease the sensitivity to disruptions. Accurate robustness measures are needed to determine if a timetable is sufficiently robust and suggest where improvements should be made.Existing robustness measures are useful when comparing different timetables with respect to robustness. They are, however, not as useful for suggesting precisely where and how robustness should be increased. In this paper, we propose a new robustness measure that incorporates the concept of critical points. This concept can be used in the practical timetabling process to find weaknesses in a timetable and to provide suggestions for improvements. In order to quantitatively assess how crucial a critical point may be, we have defined the measure robustness in critical points (RCP). In this paper, we present results from an experimental study where a benchmark of several measures as well as RCP has been done. The results demonstrate the relevance of the concept of critical points and RCP, and how it contributes to the set of already defined robustness measures
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| 6. |
- Backåker, Lars, 1984-
(författare)
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The Influence of Customer Agreements and Planning Principles on Rail Freight Performance
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Rail freight transportation is recognized worldwide as a suitable transportation mode when it comes to long haul transportation of heavy commodities. The industry is also known to be capital intensive, highly dependent on infrastructural developments and requires thorough planning of operations. Despite intensive planning of operations, great challenges remain in how to make best use of existing resources. Especially uncertainties related to up-coming daily freight volumes stand as central causes behind such planning challenges. This thesis focuses on rail freight carload transportation and concerns how customer commitments influence operational performance as well as potentials for improvements of operational planning principles. Problem statements are addressed using three separate studies and all experiments involve quantitative approaches. The first study investigates effects of a potential Volume Variation Allowance (VVA) policy through simulation. The policy dictates how much freight volumes are allowed to vary by day of week. Results indicate that effects of the policy are relatively small, but an overall decrease in transportation times is observed. The study also identifies improvement potentials with respect to the current operational planning principles used within Swedish railways. The second study proposes a new optimization-based approach for trip plan generation. The approach, including a number of extensions, is evaluated against the current industry practice. Results confirm the potentials for reduced transportation times, shunting activities as well as service frequencies. All experiments satisfy existing customer commitments. The third study explores effects of a Fixed Carload Capacity (FCC) concept which partially allows capacity reservation on services. The study adopts an extension of the previously developed optimization approach. Results confirm the hypothetical trade-off between customer groups and the dependency on capacity reservation levels, but indicate that the concept has relatively small effects with respect to regular carload customers. On the other hand, benefits in terms of guarantee of service and reliability in transportation times can be observed for the customer under the agreement.
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| 7. |
- Carlson, Annelie, 1969-, et al.
(författare)
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Nuvarande förutsättningar och försök med längre godståg mellan Gävle och Malmö
- 2014
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Andra delprojektet av ELVIS-demonstrationsprojektet för längre och tyngre godståg syftar till att analysera dagens förutsättningar för användningen av längre tåg och att utvärdera demonstrationsförsöket där ett 730 meter långt demonstrationståg (i stället för dagens maximala 630 meter) kördes mellan Gävle och Malmö 6–7 oktober 2012. En slutsats är att det är tekniskt möjligt att trafikera tåg som är längre än 630 meter men det finns organisatoriska hinder. För att utnyttja infrastrukturen effektivare, föreslår projektet som en temporär lösning användningen av dedikerade kanaler för längre godståg i specifika korridorer. Jämförelsen av demonstrationstågets färd med upp till 630 meter långa referenståg, försvårades mycket av att centrala data som beskriver referenstågen var svåra att få tag på och delvis osäkra. En viktig slutsats är att det behövs en bättre kartläggning av nuläget för att kunna göra tillförlitliga kvantitativa analyser. Det var möjligt att sammanställa information om elförbrukningen per bruttotonkilometer för demonstrationståget och 85 referenståg. Däremot är det svårt att kvantifiera hur exakt tågens längd, vikt, hastighet och antal stopp med mera, påverkar elförbrukningen var för sig – både med hänsyn till det bristfälliga datamaterialet och det faktum att det finns en relativt stor variation i elförbrukningen oavsett vilken aspekt som studerats. Betydelse av topografin och tågets längd och vikt för elförbrukningen per bruttotonkilometer kan visas. Demonstrationstågets elförbrukning per bruttotonkilometer är generellt sett lågt i jämförelse med referenstågen. Det går dock att dra slutsatsen att elförbrukningen per bruttotonkilometer generellt inte är högre för längre tåg men det går inte att säga att förbrukningen generellt är lägre. Litteraturen och diskussioner med företagen indikerar att näringslivets transportkostnader per transporterat ton gods kan reduceras genom att använda längre godståg. Skalfördelarna kan dock enbart utnyttjas om inte hela lokets dragkraft utnyttjas redan idag. Det är uppenbart att den tillgängliga järnvägsinfrastrukturen avgör vilka tåglängder och -vikter som är affärsmässigt gångbara. Elkostnaderna per transporterat ton kan möjligtvis också reduceras genom att använda längre tåg, men detta kan inte förutsättas utan vidare. En trafikering av längre godståg i större omfattning kräver investeringar i mötesspår, förbigångsspår, terminalspår med mera. De hittills genomförda överslagsmässiga kalkylerna för 750 meter långa tåg tyder på att investeringskostnaderna är relativt blygsamma. Det finns behov av analyser för olika tåglängder eftersom det inte är uppenbart att minimilängden på 750 meter, som krävs på TEN-T:s stomnät från 2030, är optimal.
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| 8. |
- Gestrelius, Sara
(författare)
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Mathematical models for optimising decision support systems in the railway industry
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- After the deregulation of the Swedish railway industry, train operating companies compete for and on the same infrastructure. This makes the allocation of rail capacity a most delicate problem, and for a well-functioning railway system the allocation must be fair, efficient and functional. The capacity allocation tasks include e.g. constructing the yearly timetable and making track allocation plans for rail yards. The state of practice is that experienced planners construct the schedules manually with little or no decision support. However, as the planners are often faced with large combinatorial problems that are notoriously hard to solve there is a great potential in implementing optimising decision support systems. The research presented in this licentiate thesis aims at developing and examining mathematical models and methods that could be part of such support systems. The thesis focuses on two planning problems in particular, and the presented methods have been developed especially for the Swedish railway system. First of all, a model for optimising a train timetable with respect to robustness is presented. The model tries to increase the number of alternative meeting locations that can be used in a disturbed traffic situation and has an execution time of less than 5 minutes when solving the problem for the track section between Boden and Vännäs. Secondly, the problem of generating efficient classification bowl schedules for shunting yards is examined. The aim is to find the track allocation that minimises the number of required shunting movements while still respecting all operational, physical and time constraints imposed by the yard. Three optimisation models are presented, and simple planning rules are also investigated. The methods are tested on historic data from Hallsberg, the largest shunting yard in Sweden, and the results show that while the simple planning rules are not adequate for planning the classification bowl, two of the optimisation models consistently return an optimal solution within an acceptable execution time.
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| 9. |
- Gholami, Omid, 1979-, et al.
(författare)
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A Heuristic Approach to Solving the Train Traffic Re-Scheduling Problem in Real Time
- 2018
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Ingår i: Algorithms. - : MDPI. - 1999-4893. ; 11:4, s. 1-18
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Tidskriftsartikel (refereegranskat)abstract
- Effectiveness in managing disturbances and disruptions in railway traffic networks, when they inevitably do occur, is a significant challenge, both from a practical and theoretical perspective. In this paper, we propose a heuristic approach for solving the real-time train traffic re-scheduling problem. This problem is here interpreted as a blocking job-shop scheduling problem, and a hybrid of the mixed graph and alternative graph is used for modelling the infrastructure and traffic dynamics on a mesoscopic level. A heuristic algorithm is developed and applied to resolve the conflicts by re-timing, re-ordering, and locally re-routing the trains. A part of the Southern Swedish railway network from Karlskrona centre to Malmö city is considered for an experimental performance assessment of the approach. The network consists of 290 block sections, and for a one-hour time horizon with around 80 active trains, the algorithm generates a solution in less than ten seconds. A benchmark with the corresponding mixed-integer program formulation, solved by commercial state-of-the-art solver Gurobi, is also conducted to assess the optimality of the generated solutions.
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| 10. |
- Grahn, Håkan, et al.
(författare)
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A Parallel Re-Scheduling Algorithm for Railway Traffic Disturbance Management --- Initial Results
- 2011
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Konferensbidrag (refereegranskat)abstract
- In Sweden, the railway traffic and demand for track capacity have increased significantly the last years resulting in a high traffic density where even small disturbances propagate. This makes it hard for the traffic managers to overview the consequences of disturbances and their decisions when rescheduling the traffic. In previous research, we have developed and experimentally evaluated a greedy depthfirst search algorithm. This algorithm aims to support the traffic managers by computing alternative rescheduling solutions in order to minimize the train delays. The simulation experiments were based on real traffic data and the algorithm proved to be very effective for many types of disturbances and delivers optimal or close to optimal solutions in a few seconds. However, the experiments also indicated a need for improvements when solving more severe disturbances related to major infrastructure failures. The improvements concern primarily the need to explore larger parts of the search space quickly and to branch more effectively by avoiding exploring non-promising nodes. This paper presents results from an analysis of where and when successful branching decisions are made. The analysis showed that the successful branching decisions were generally made quite far down in the search space tree, but somewhat higher up during more severe disturbance scenarios. We also present an improved version of the greedy algorithm and a parallel implementation of it. The parallelization is composed of eight different threads allocated to one processor each starting to branch at the highest branching level. The experimental results show that it improves the solutions for difficult disturbance scenarios.
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| 11. |
- Iqbal, Syed Muhammad Zeeshan, et al.
(författare)
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A Parallel DFS Algorithm for Train Re-scheduling During Traffic Disturbances — Early Results
- 2011
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Konferensbidrag (refereegranskat)abstract
- Railways are an important part of the infrastructure in most countries. As the railway networks become more and more saturated, even small traffic disturbances can propagate and have severe consequences. In this paper, the train re-scheduling problem is studied in order to minimize the final delay for all trains in the scenarios. We propose a parallel algorithm based on a depth-first search branch-and-bound strategy. The parallel algorithm is compared to a sequential algorithm in terms of the quality of the solution and the number of nodes evaluated, as well as to optimal solutions found by Cplex, using 20 disturbance scenarios. Our parallel algorithm significantly improves the solution for 5 out of 20 disturbance scenarios, as compared to the sequential algorithm.
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| 12. |
- Iqbal, Syed Muhammad Zeeshan, et al.
(författare)
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A parallel heuristic for fast train dispatching during railway traffic disturbances : Early results
- 2012
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Konferensbidrag (refereegranskat)abstract
- Railways are an important part of the infrastructure in most countries. As the railway networks become more and more saturated, even small traffic disturbances can propagate and have severe consequences. Therefore, efficient re-scheduling support for the traffic managers is needed. In this paper, the train real-time re-scheduling problem is studied in order to minimize the total delay, subject to a set of safety and operational constraints. We propose a parallel greedy algorithm based on a depth-first branch-and-bound search strategy. A number of comprehensive numerical experiments are conducted to compare the parallel implementation to the sequential implementation of the same algorithm in terms of the quality of the solution and the number of nodes evaluated. The comparison is based on 20 disturbance scenarios from three different types of disturbances. Our results show that the parallel algorithm; (i) efficiently covers a larger portion of the search space by exchanging information about improvements, and (ii) finds better solutions for more complicated disturbances such as infrastructure problems. Our results show that the parallel implementation significantly improves the solution for 5 out of 20 disturbance scenarios, as compared to the sequential algorithm.
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| 13. |
- Iqbal, Syed Muhammad Zeeshan, et al.
(författare)
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Multi-Strategy Based Train Re-Scheduling During Railway Traffic Disturbances
- 2013
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Konferensbidrag (refereegranskat)abstract
- Disruptions and delays in railway traffic networks due to different types of disturbances is a frequent problem in many countries. When disruptions occur, the train traffic dispatchers may need to re-schedule the traffic and this is often a very demanding and complicated task. To support the train traffic dispatchers, we propose to use a parallelized multi-strategy based greedy algorithm. This paper presents three different parallelization approaches: (i) Single Strategy with a Partitioned List (i.e. the parallel processes originate from different starting points), (ii) Multiple Strategies with a Non-Partitioned List, and (iii) Multiple Strategies with a Partitioned List. We present an evaluation for a busy part of the Swedish railway network based on performance metrics such as the sum of all train delays at their final destinations and the number of delayed trains. The results show that parallelization helps to improve the solution quality. The parallel approach (iii) that combines all re-scheduling strategies with a partitioned list performs best among the three parallel approaches when minimizing the total final delay. The main conclusion is that the multi-strategy based parallel approach significantly improves the solution for 11 out of 20 disturbance scenarios, as compared to the sequential re-scheduling algorithm. The approach also provides an increased stability since it always delivers a feasible solution in short time.
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| 14. |
- Joborn, Martin, et al.
(författare)
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Description of a decision support tool aimed at advanced Real Time Network Management and requirements for a demonstrator
- 2020
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In this report we outline a conceptual demonstrator for advanced real time network management for freight rail traffic. The focus is on the coordination between traffic control, train drivers and yard management, three essential parts in the real time management of a rail freight network. The intention is that the demonstrator can support multiple purposes, such as education and training, demonstrating research advancements, and enabling feedback between practitioners, system developers and researchers. The proposed demonstrator has a focus on the interaction between different systems and between humans using these systems, but also on the rail freight system perspective by the inclusion of the connection between the line and the yard. We present a generic architecture and propose existing components that could be combined to such a demonstrator. Thus, even though the demonstrator may seem complex and visionary, the existence of these components makes the realization of the demonstrator realistic. The development roadmap for the demonstrator proposes both a step-wise implementation plan of the complete demonstrator, as well as several partial packages that provide useful sub-demonstrators by themselves.The appendices of the report include contributions to the continued development of two of the components that are part of the demonstrator. Firstly, in order to also better understand the type of situations that yard managers need to handle in operations and what implications these have on the traffic on the line, a Swedish case study has been conducted and the results are presented in Appendix A. More specifically, the case study analyses the factors that influence the departure time deviation for freight trains and how these can be used for predicting the actual departure time. These predictions can be used in a decision support system for yard planning at larger marshalling yards. A conclusion is that no single factor can fully explain the departure time deviation, but many different factors contribute to it, like destination, time of day, train load, number of wagons on the yard, connection time for wagons, and connection time for locomotives.Secondly, to support the traffic controllers and dispatchers with an advanced decision support tool for deviation handling, a selection of different functionalities and algorithms may be required. In Appendix B, two different approaches for disturbance management are presented. Approach 1 (ALG1) is a heuristic, parallel algorithm, while the second approach (ALG2) is an exact algorithm based on state-of-the-art commercial optimization software. In order to classify and evaluate alternative algorithms for train re-scheduling and disturbance management, an assessment framework is also proposed in Appendix B. Based on this framework, the overall strengths and shortcomings of the two mentioned train rescheduling algorithms are assessed while applied on a set of 30 simulated disturbance scenarios of various complexity. The results show that typically, ALG2 obtained good rescheduling solutions for all 30 disturbances, but compared to ALG1, ALG2 is slow in obtaining solutions.ALG1 is good at quickly finding solutions with less passenger delays while it is less effective when it is used to solve disturbances associated with an infrastructure failure. The strength of ALG2 is its ability to reschedule the traffic during infrastructure failures. A detailed presentation of the evaluation is found in Appendix B.
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| 15. |
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| 16. |
- Josyula, Sai Prashanth, 1992-, et al.
(författare)
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A parallel algorithm for train rescheduling
- 2018
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Ingår i: Transportation Research Part C. - : Elsevier. - 0968-090X .- 1879-2359. ; 95, s. 545-569
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Tidskriftsartikel (refereegranskat)abstract
- One of the crucial factors in achieving a high punctuality in railway traffic systems, is the ability to effectively reschedule the trains when disturbances occur. The railway traffic rescheduling problem is a complex task to solve both from a practical and a computational perspective. Problems of practically relevant sizes have typically a very large search space, making them time-consuming to solve even for state-of-the-art optimization solvers. Though competitive algorithmic approaches are a widespread topic of research, not much research has been done to explore the opportunities and challenges in parallelizing them. This paper presents a parallel algorithm to efficiently solve the real-time railway rescheduling problem on a multi-core parallel architecture. We devised (1) an effective way to represent the solution space as a binary tree and (2) a novel sequential heuristic algorithm based on a depth-first search (DFS) strategy that quickly traverses the tree. Based on that, we designed a parallel algorithm for a multi-core architecture, which proved to be 10.5 times faster than the sequential algorithm even when run on a single processing core. When executed on a parallel machine with 8 cores, the speed further increased by a factor of 4.68 and every disturbance scenario in the considered case study was solved within 6 s. We conclude that for the problem under consideration, though a sequential DFS approach is fast in several disturbance scenarios, it is notably slower in many other disturbance scenarios. The parallel DFS approach that combines a DFS with simultaneous breadth-wise tree exploration, while being much faster on an average, is also consistently fast across all scenarios.
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| 17. |
- Josyula, Sai Prashanth, 1992-, et al.
(författare)
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An evaluation framework and algorithms for train rescheduling
- 2020
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Ingår i: Algorithms. - : MDPI AG. - 1999-4893. ; 13:12
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Tidskriftsartikel (refereegranskat)abstract
- In railway traffic systems, whenever disturbances occur, it is important to effectively reschedule trains while optimizing the goals of various stakeholders. Algorithms can provide significant benefits to support the traffic controllers in train rescheduling, if well integrated into the overall traffic management process. In the railway research literature, many algorithms are proposed to tackle different versions of the train rescheduling problem. However, limited research has been performed to assess the capabilities and performance of alternative approaches, with the purpose of identifying their main strengths and weaknesses. Evaluation of train rescheduling algorithms enables practitioners and decision support systems to select a suitable algorithm based on the properties of the type of disturbance scenario in focus. It also guides researchers and algorithm designers in improving the algorithms. In this paper, we (1) propose an evaluation framework for train rescheduling algorithms, (2) present two train rescheduling algorithms: a heuristic and a MILP-based exact algorithm, and (3) conduct an experiment to compare the two multi-objective algorithms using the proposed framework (a proof-of-concept). It is found that the heuristic algorithm is suitable for solving simpler disturbance scenarios since it is quick in producing decent solutions. For complex disturbances wherein multiple trains experience a primary delay due to an infrastructure failure, the exact algorithm is found to be more appropriate. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.
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| 18. |
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| 19. |
- Josyula, Sai Prashanth, 1992-
(författare)
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Parallel algorithms for real-time railway rescheduling
- 2019
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In railway traffic systems, it is essential to achieve a high punctuality to satisfy the goals of the involved stakeholders. Thus, whenever disturbances occur, it is important to effectively reschedule trains while considering the perspectives of various stakeholders. The train rescheduling problem is a complex task to solve, both from a practical and a computational perspective. From the latter perspective, a reason for the complexity is that the rescheduling solution(s) of interest may be dispersed across a large solution space. This space needs to be navigated fast while avoiding portions leading to undesirable solutions and exploring portions leading to potentially desirable solutions. The use of parallel computing enables such a fast navigation of the search tree. Though competitive algorithmic approaches for train rescheduling are a widespread topic of research, limited research has been conducted to explore the opportunities and challenges in parallelizing them.This thesis presents research studies on how trains can be effectively rescheduled while considering the perspectives of passengers along with that of other stakeholders. Parallel computing is employed, with the aim of advancing knowledge about parallel algorithms for solving the problem under consideration.The presented research contributes with parallel algorithms that reschedule a train timetable during disturbances and studies the incorporation of passenger perspectives during rescheduling. Results show that the use of parallel algorithms for train rescheduling improves the speed of solution space navigation and the quality of the obtained solution(s) within the computational time limit.This thesis consists of an introduction and overview of the work, followed by four research papers which present: (1) A literature review of studies that propose and apply computational support for train rescheduling with a passenger-oriented objective; (2) A parallel heuristic algorithm to solve the train rescheduling problem on a multi-core parallel architecture; (3) A conflict detection module for train rescheduling, which performs its computations on a graphics processing unit; and (4) A redesigned parallel algorithm that considers multiple objectives while rescheduling.
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| 20. |
- Josyula, Sai Prashanth, 1992-
(författare)
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Parallel algorithms for solving the train timetable rescheduling problem
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In railways, it is essential to achieve high train punctuality. Thus, whenever disturbances occur, it is important to reschedule the trains effectively. This task is typically handled manually by traffic controllers in real-time. This thesis presents efficient computer algorithms for assisting traffic controllers in effectively rescheduling a train timetable during disturbances.The train timetable rescheduling problem is typically hard to solve as the solutions of interest, spread across a vast solution space, need to be searched quickly. Two main solution approaches involve using (i) exact algorithms, which typically search the entire solution space, and (ii) heuristic algorithms, which try to search for a good-enough solution quickly. Although research on competitive algorithms is prevalent, limited research exists on exploring the benefits and challenges of using parallel computing to tackle the problem.The primary objectives of this thesis are: (i) to model the train timetable rescheduling problem's search tree to be well-suited for parallel computing, (ii) to devise parallel heuristic search algorithms that can quickly and effectively solve the problem for one or many rescheduling objectives, (iii) to investigate the potential and limitations of parallel computing in the context of the problem, (iv) to investigate the comparison and evaluation of alternative solution approaches to analyze their strengths and limitations.In this thesis, we model the problem's search tree as a binary tree where the edges represent alternative rescheduling decisions and leaf nodes represent feasible timetables. We solve the problem by searching the tree using a parallel strategy that combines a depth-first search with simultaneous breadth-wise tree exploration. We evaluate our parallel algorithms for various disturbances on a Swedish railway network through experiments.The results of our research show that a parallel depth-first search algorithm can quickly search the devised search tree for solutions. With multiple rescheduling objectives, the parallel search algorithm obtained better solutions and showed higher speedups. Additional problem constraints often improved the search process by making the parallel algorithm reach the solutions faster. The results also show the potential and challenges of using graphics processing units for detecting conflicts in the timetable during the search. In conclusion, this thesis shows that parallel train timetable rescheduling algorithms can improve the search speed and the quality of the solution(s) obtained in real-time within the computational time limit.
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| 21. |
- Josyula, Sai Prashanth, 1992-, et al.
(författare)
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Parallel computing for multi-objective train rescheduling
- 2021
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Ingår i: IEEE Transactions on Emerging Topics in Computing. - : IEEE Computer Society. - 2168-6750. ; 9:4, s. 1683-1696
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Tidskriftsartikel (refereegranskat)abstract
- In railway traffic systems, it is essential to achieve a high punctuality to satisfy the goals of the involved stakeholders. Thus, whenever disturbances occur, it is important to effectively reschedule trains while considering the perspectives of various stakeholders. This typically involves solving a multi-objective train rescheduling problem, which is much more complex than its single-objective counterpart. Solving such a problem in real-time for practically relevant problem sizes is computationally challenging. The reason is that the rescheduling solution(s) of interest are dispersed across a large search tree. The tree needs to be navigated fast while pruning off branches leading to undesirable solutions and exploring branches leading to potentially desirable solutions. The use of parallel computing enables such a fast navigation of the tree. This paper presents a heuristic parallel algorithm to solve the multi-objective train rescheduling problem. The parallel algorithm combines a depth-first search with simultaneous breadth-wise tree exploration while searching the tree for solutions. An existing parallel algorithm for single-objective train rescheduling has been redesigned, primarily, by (i) pruning based on multiple metrics, and (ii) maintaining a set of upper bounds. The redesign improved the quality of the obtained rescheduling solutions and showed better speedups for several disturbance scenarios. CCBY
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| 22. |
- Josyula, Sai Prashanth, 1992-, et al.
(författare)
-
Passenger-oriented Railway Traffic Re-scheduling : A Review of Alternative Strategies utilizing Passenger Flow Data
- 2017
-
Konferensbidrag (refereegranskat)abstract
- Developing and operating seamless, attractive and efficient public transport services in a liberalized market requires significant coordination between involved actors, which is both an organizational and technical challenge. During a journey, passengers often transfer between different transport services. A delay of one train or a bus service can potentially cause the passenger to miss the transfer to the subsequent service. If those services are provided by different operators and those are not coordinated and the information about the services are scattered, the passengers will suffer. In order to incorporate the passenger perspective in the re-scheduling of railway traffic and associated public transport services, the passenger flow needs to be assessed and quantified. We therefore perform a survey of previous research studies that propose and apply computational re-scheduling support for railway traffic disturbance management with a passenger-oriented objective. The analysis shows that there are many different ways to represent and quantify the effects of delays on passengers, i.e.“passenger inconvenience”. In the majority of the studies, re-scheduling approaches rely on historic data on aggregated passenger flows, which are independent of how the public transport services are re-scheduled. Few studies incorporate a dynamic passenger flow model that reacts based on how the transport services are re-scheduled. None of the reviewed studies use real-time passenger flow data in the decision-making process. Good estimations of the passenger flows based on historic data are argued to be sufficient since access to large amounts of passenger flow data and accurate prediction models is available today.
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| 23. |
- Khoshniyat, Fahimeh, 1981-, et al.
(författare)
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An Optimization Approach for On-Demand Railway Slot Allocation
- 2017
-
Konferensbidrag (refereegranskat)abstract
- This paper addresses a significant challenge experienced by infrastructure managers concerninghandling and scheduling slot requests for additional trains, or urgent track maintenance,after the master timetable has been finalized. In congested railway networks, wherepassenger trains share the tracks with freight trains and where the freight train operatorscannot fully predict the actual need for access to train slots long in advance, there is aneed for a flexible and effective timetabling revision process. Since the re-scheduling oftraffic and maintenance is a demanding task, the benefits of using computational schedulingsupport is evident. From the perspective of an infrastructure manager, we propose andexperimentally evaluate an optimization-based approach for assessment and scheduling ofadditional slot requests. When inserting several trains, the relations between time and routeoverlap as well as direction of trains, and the required computation time are investigated.The optimization-based approach relies on a Mixed Integer Linear Programming formulation.In this model, the explicit capacity restrictions of line segments and station tracks,including track and platform length, are considered. This model also permits bidirectionaltraffic on all lines where relevant. The experimental results show that optimal solutions canbe retrieved quickly in many scenarios, while for certain scenarios the proposed approachis too time-consuming. The required computation time is very dependent on the propertiesof the inserted train and maintenance slots, respectively.
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| 24. |
- Khoshniyat, Fahimeh, 1981-, et al.
(författare)
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Analysis of strengths & weaknesses of a MILP model for revising railway traffic timetables
- 2017
-
Ingår i: OpenAccess Series in Informatics. - Dagstuhl, Germany : Schloss Dagstuhl- Leibniz-Zentrum fur Informatik GmbH, Dagstuhl Publishing. - 9783959770422
-
Konferensbidrag (refereegranskat)abstract
- A railway timetable is typically planned one year in advance, but may be revised several times prior to the time of operation in order to accommodate on-demand slot requests for inserting additional trains and network maintenance. Revising timetables is a computationally demanding task, given the many dependencies and details to consider. In this paper, we focus on the potential of using optimization-based scheduling approach for revising train timetables during short term planning, from one week to few hours before the actual operation. The approach relies on a MILP (Mixed Integer Linear Program) model which is solved by using the commercial solver Gurobi. In a previous experimental study, the MILP approach was used to revise a significant part of the annual timetable for a sub-network in Southern Sweden to insert additional trains and allocate time slots for urgent maintenance. The results showed that the proposed MILP approach in many cases generates feasible, good solutions rather fast. However, proving optimality was in several cases time-consuming, especially for larger problems. Thus, there is a need to investigate and develop strategies to improve the computational performance. In this paper, we present results from a study, where a number of valid inequalities has been selected and applied to the MILP model with the aim to reduce the computation time. The experimental evaluation of the selected valid inequalities showed that although they can provide a slight improvement with respect to computation time, they are also weakening the LP relaxation of the model.
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| 25. |
- Khoshniyat, Fahimeh
(författare)
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Optimization-Based Methods for Revising Train Timetables with Focus on Robustness
- 2016
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With increase in the use of railway transport, ensuring robustness in railway timetables has never been this important. In a dense railway timetable even a small disturbance can propagate easily and affect trains' arrival and departure times. In a robust timetable small delays are absorbed and knock-on effects are prevented effectively. The aim of this thesis is to study how optimization tools can support the generation of robust railway traffic timetables. We address two Train Timetabling Problems (TTP) and for both problems we apply Mixed Integer Linear Programming (MILP) to solve them from network management perspectives. The first problem is how robustness in a given timetable can be assessed and ensured. To tackle this problem, a headway-based method is introduced. The proposed method is implemented in real timetables and evaluated from performance perspectives. Furthermore, the impact of the proposed method on capacity utilization, heterogeneity and the speed of trains, is monitored. Results show that the proposed method can improve robustness without imposing major changes in timetables. The second problem addressed in the thesis is how robustness can be assessed and maintained in a given timetable when allocating additional traffic and maintenance slots. Different insertion strategies are studied and their consequences on capacity utilization and on the properties of the timetables are analyzed. Two different insertion strategies are considered: i) simultaneous and ii) stepwise insertion. The results show that inserting the additional trains simultaneously usually results in generating more optimal solutions. However, solving this type of problem is computationally challenging. We also observed that the existing robustness metrics cannot capture the essential properties of having more robust timetables. Therefore we proposed measuring Channel Width, Channel Width Forward, Channel Width Behind and Track Switching.Furthermore, the experimental analysis of the applied MILP model shows that some cases are computationally hard to solve and there is a need to decrease the computation time. Hence several valid inequalities are developed and their effects on the computation time are analyzed.This thesis contains three papers which are appended. The results of this thesis are of special interests for railway traffic planners and it would support their working process. However, railway traffic operators and passengers also benefit from this study.
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| 26. |
- Krasemann, Johanna Törnquist
(författare)
-
Design of an effective algorithm for fast response to the re-scheduling of railway traffic during disturbances
- 2012
-
Ingår i: Transportation Research Part C. - : Elsevier. - 0968-090X .- 1879-2359. ; 20:1, s. 62-78
-
Tidskriftsartikel (refereegranskat)abstract
- An attractive and sustainable railway traffic system is characterized by having a high security, high accessibility, high energy performance and offering reliable services with sufficient punctuality. At the same time, the network is to be utilized to a large extent in a cost-effective way. This requires a continuous balance between maintaining a high utilization and sufficiently high robustness to minimize the sensitivity to disturbances. The occurrence of some disturbances can be prevented to some extent but the occurrence of unpredictable events are unavoidable and their consequences then need to be analyzed, minimized and communicated to the affected users. Valuable information necessary to perform a complete consequence analysis of a disturbance and the re-scheduling is however not always available for the traffic managers. With current conditions, it is also not always possible for the traffic managers to take this information into account since he or she needs to act fast without any decision-support assisting in computing an effective re-scheduling solution. In previous research we have designed an optimization-based approach for re-scheduling which seems promising. However, for certain scenarios it is difficult to find good solutions within seconds. Therefore, we have developed a greedy algorithm which effectively delivers good solutions within the permitted time as a complement to the previous approach. To quickly retrieve a feasible solution the algorithm performs a depth-first search using an evaluation function to prioritise when conflicts arise and then branches according to a set of criteria.
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| 27. |
- Krasemann, Johanna Törnquist
(författare)
-
Design of an Effective Algorithm for Fast Response to the Rescheduling of Railway Traffic During Disturbances
- 2009
-
Konferensbidrag (refereegranskat)abstract
- The increased occurrence of railway traffic disturbances shows that effective re-scheduling is important. In previous research we have designed an optimization-based approach which seems promising. However, for some scenarios it is difficult to find good solutions within seconds. Therefore, we have developed a greedy algorithm which effectively delivers good solutions within the permitted time. To quickly retrieve a feasible solution the algorithm performs a depth-first search using an evaluation function to prioritise when conflicts arise and then branches according to a set of criteria.
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| 28. |
- Krasemann, Johanna Törnquist
(författare)
-
Greedy algorithm for railway traffic re-scheduling during disturbances : a Swedish case
- 2010
-
Ingår i: IET Intelligent Transport Systems. - : The Institution of Engineering and Technology. - 1751-956X .- 1751-9578. ; 4:4
-
Tidskriftsartikel (refereegranskat)abstract
- The positive trend of increased use of railway transportation in Europe has resulted in an increased sensitivity to and occurrence of traffic disturbances. In addition to the need for extensions of the infrastructure, the need to effectively limit and predict the effects of disturbances becomes apparent. The kernel of the disturbance management problem is to revise the original timetable in line with the new conditions and decide where, when and how trains should overtake or meet to minimise the negative effect of the disturbance. In previous research, the author has designed optimisation-based approach for rescheduling, which seems promising, but for some scenarios it is difficult to find good solutions within seconds. Also, more detailed constraints will have to be included, which makes the problem even more complex and difficult to solve. Therefore the author developed a greedy algorithm that effectively delivers good solutions within the permitted time. To quickly retrieve a feasible solution, the algorithm performs a depth-first search using an evaluation function to prioritise when conflicts arise and then branches according to a set of criteria. A performance analysis of the algorithm was carried out using simulated experiments showing its strengths and weaknesses.
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| 29. |
- Krasemann, Johanna Törnquist
(författare)
-
Pros and cons of increased complexity in re-scheduling strategies for railway traffic disturbances : A Swedish case
- 2009
-
Konferensbidrag (refereegranskat)abstract
- The positive trend of increased use of both railway passenger and freight transportation in Europe has resulted in an increased sensitivity to and occurrence of traffic disturbances. In addition to the need for extensions of the infrastructure, the need to effectively limit and predict the effects of disturbances becomes apparent. The abilities to maximise the use of available infrastructure such as sidings and platforms as well as the tracks in both directions is therefore critical. The kernel of the disturbance management problem is to revise the original timetable in line with the new conditions and decide where, when and how trains should overtake or meet to minimise the negative effect of the disturbance. There exist both sophisticated and simple models and methods which have different strengths and weaknesses. This paper presents results from a Swedish research project and investigates the pros and cons of different re-scheduling models and methods.
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| 30. |
- Lamorgese, Leonardo, et al.
(författare)
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Train Dispatching
- 2018. - 268
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Ingår i: Handbook of Optimization in the Railway Industry. - Cham : Springer New York LLC. - 9783319721538 ; , s. 265-283
-
Bokkapitel (refereegranskat)abstract
- Train rescheduling problems have received significant attention in the operations research community during the past 20–30 years. These are complex problems with many aspects and constraints to consider. This chapter defines the problem and summarizes the variety of model types and solution approaches developed over the years, in order to address and solve the train dispatching problem from the infrastructure manager perspective. Despite all the research efforts, it is, however, only very recently that the railway industry has made significant attempts to explore the large potential in using optimization-based decision-support to facilitate railway traffic disturbance management. This chapter reviews state-of-practice and provides a discussion about the observed slow progress in the application of optimization-based methods in practice. A few successful implementations have been identified, but their performance as well as the lessons learned from the development and implementation of those system are unfortunately only partly available to the research community, or potential industry users. © 2018, Springer International Publishing AG.
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| 31. |
- Peterson, Anders, Docent, 1976-, et al.
(författare)
-
Deliverable D 3.1: Analysis of the gap between daily timetable and operational traffic
- 2019
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Fr8Rail II/Work-Package 3 Real-time network management and improved methods for timetable planning addresses the problem to improve capacity and punctuality in the railway system by developing concepts and methods for tactical planning and operational traffic. In this report the state-of-the-art has been summarised.The aim of the project is to:Propose concepts and methods that improve the annual and short-term timetable planning.Demonstrate how the proposed timetable planning concepts improve the prerequisites for real-time network management.Develop methods and tools that can reduce inefficiencies in real time network management.An important aspect is to improve the coordination between yards/terminals and the line network, and between Infrastructure Manager, Yard Managers, and freight Rail Undertakings.We motivate our research by the current situation in Sweden, which is characterised by low on-time performance for freight trains, dense and heterogenous traffic on the major railway lines, and a rigid annual timetabling process, which is non-suitable for short-term changes. We believe that better tools for network planning and management on tactical and operational level can help to connect planning and operational processes.Aiming for improvements of the operational traffic, there is a need for systematic development of methods applied at several planning horizons, based on both simulation and optimization techniques. Close to operation fast methods are needed, for example, based on meta-heuristics.The maintenance planning process and improvement potential have been described. This is a new piece of the puzzle and it is important to close the gap between timetable planning and operational traffic. The different planning processes at the Infrastructure Manager, the Rail Undertakings and the Maintenance Contractors should be aligned.When developing new approaches for computational decision-support tools for real-time network management, it is important — but very challenging — to evaluate and benchmark with existing software tools. We also observe that the research stream on computational decision-support and algorithm development for railway traffic management has not yet been sufficiently merged with the corresponding research stream focusing on aspects of human computer interaction.
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| 32. |
- Ramstedt, Linda, et al.
(författare)
-
Movement of people and goods
- 2013
-
Ingår i: Understanding Complex Systems. - Cham : Springer Verlag. - 9783540938125 - 9783540938132 ; , s. 705-720
-
Bokkapitel (refereegranskat)abstract
- Due to the continuous growth of traffic and transportation and thus an increased urgency to analyze resource usage and system behavior, the use of computer simulation within this area has become more frequent and acceptable. This chapter presents an overview of modeling and simulation of traffic and transport systems and focuses in particular on the imitation of social behavior and individual decision-making in these systems. We distinguish between transport and traffic. Transport is an activity where goods or people are moved between points A and B, while traffic is referred to as the collection of several transports in a common network such as a road network. We investigate to what extent and how the social characteristics of the users of these different traffic and transport systems are reflected in the simulation models and software. Moreover, we highlight some trends and current issues within this field and provide further reading advice. © 2017, Springer International Publishing AG.
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| 33. |
- Ramstedt, Linda, et al.
(författare)
-
Movement of People and Goods
- 2013
-
Ingår i: Simulating Social Complexity. - Berlin, Heidelberg : Springer. - 9783540938125 - 9783540938132 ; , s. 651-665
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Due to the continuous growth of traffic and transportation and a thus increased urgency to analyze resource usage and system behavior, the use of computer simulation within this area has become more frequent and acceptable. This chapter presents an overview of modeling and simulation of traffic and transport systems, and focuses in particular on the imitation of social behavior and individual decision making in these systems. We distinguish between transport and traffic. Transport is an activity where goods or people are moved between points A and B while traffic is referred to as the collection of several transports in a common network such as a road network. We investigate to what extent and how the social characteristics of the users of these different traffic and transport systems are reflected in the simulation models and software. Moreover, we highlight some trends and current issues within this field and provide further reading advice.
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| 34. |
- Rydergren, Clas, 1972-, et al.
(författare)
-
Unravelling travel flow dynamics: A multi-level analysis of public transport demand and passenger reliability
- 2018
-
Konferensbidrag (refereegranskat)abstract
- Smart cities and communities rely on efficient, reliable and robust transport systems. Managing urban public transport systems is becoming increasingly challenging with a pronounced shift towards multiple actors operating in a multi-modal multi-level networks. This calls for the development of an integrated passenger-focused management approach which takes advantage of multiple data sources and state-of-the-art scheduling support. The TRANS-FORM project is developing, implementing and testing a data driven decision making tool that will support smart planning and proactive and adaptive operations. The tool will integrate new concepts and methods of behavioral modelling, passenger flow forecasting and network state predictions into real-time operations. In this study we present the first step in this direction which consists of an empirical analysis of passenger flows to infer travel patterns and service reliability properties. Data mining and transport flow analysis are used to investigate network dynamics at different scales.
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| 35. |
- Törnquist Krasemann, Johanna, 1977-
(författare)
-
Computational decision-support for railway traffic management and associated configuration challenges: An experimental study
- 2015
-
Ingår i: Journal of Rail Transport Planning & Management. - : Elsevier. - 2210-9706. ; 5:3, s. 95-109
-
Tidskriftsartikel (refereegranskat)abstract
- This paper investigates potential configuration challenges in the development of optimization-based computational re-scheduling support for railway traffic networks. The paper presents results from an experimental study on how the characteristics of different situations influence the problem formulation and the resulting re-scheduling solutions. Two alternative objective functions are applied: Minimization of the delays at the end stations which exceed three minutes and minimization of delays larger than three minutes at intermediary commercial stops and at end stations. The study focuses on the congested, single-tracked Iron Ore line located in Northern Sweden. A combinatorial optimization model adapted to the special restrictions of this line is applied on 20 different disturbance scenarios and solved using commercial optimization software. The resulting re-scheduling solutions are analyzed numerically and visually in order to better understand the practical impact of using the suggested problem formulations in this context. The results show that the two alternative, objective functions result in structurally, quite different re-scheduling solutions. All scenarios were solved to optimality within 1 minute or less, which indicates that commercial solvers can handle practical problems of a relevant size for this type of setting, but the type of scenario has also a significant impact on the computation time.
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| 36. |
- Törnquist Krasemann, Johanna, 1977-
(författare)
-
Configuration of an optimization-based decision support for railway traffic management in different contexts
- 2015
-
Ingår i: 6th International Conference on Railway Operations Modelling and Analysis, Tokyo, March 23-26, 2015.
-
Konferensbidrag (refereegranskat)abstract
- This paper investigates potential configuration challenges in the development of optimization-based computational re-scheduling support for railway traffic networks. The paper presents results from an experimental study on how the characteristics of different situations and the network influence the problem formulation and the resulting re-scheduling solutions. Two alternative objective functions are applied: a) Minimization of the delays at the end stations which exceed three minutes and b) minimization of delays larger than three minutes at intermediary commercial stops and at end stations. The study focuses on the congested, single-tracked Iron Ore line located in Northern Sweden and partially Norway. A combinatorial optimization model adapted to the special restrictions of this line is applied and solved using commercial optimization software. 20 different disturbance scenarios are solved and the resulting re-scheduling solutions are analyzed numerically and visually in order to better understand their practical impact. The results show that the two alternative, but similar, objective functions result in structurally, quite different re-scheduling solutions. The results also show that the selected objective functions have some flaws when it comes to scheduling trains that are ahead of their schedule by early departure, or by having a lot of margin time due to waiting time in meeting/passing locations. These early trains are not always “pushed” forward unless the objective function promotes that in some way. All scenarios were solved to optimality within 1 minute or less, which indicates that commercial solvers can handle practical problems of a relevant size for this type of setting.
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| 37. |
- Törnquist Krasemann, Johanna, 1977-, et al.
(författare)
-
Passagerar-fokuserad hantering av störningar i den regionala tågtrafiken : En sammanställning av arbete och resultat från den svenska delen av TRANSFORM-projektet
- 2019
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Bakgrund och syfteInformationstjänster för kollektivtrafikresenärer blir allt bättre, men vid störningar är det fortfarande mycket svårt som resenär att få tillräcklig och aktuell information om hur resan kommer att kunna fullföljas. För planerare och trafikledning är det också en enorm utmaning i att skapa robusta planer som medför flexibilitet i driften, att övervaka trafikläget och att styra systemet på ett proaktivt sätt som balanserar interna prioriteringar med resenärernas. Inom projektet har vi därför studerat två alternativa principer och metoder för att omplanera tågtrafiken vid störningar – där den ena är mer resenärsfokuserad och den andra mer trafiksystem-fokuserad.MetodikDen förstnämnda metoden inkluderar i omplaneringen av tågen vid störningar även regionala bussar. Metoden beaktar resandeutbyten och alternativa resvägar för att, om möjligt, minska resenärers försening genom att samordna tåg- och/eller bussanslutningar. Här används en matematisk modell som utvecklats i projektet och optimeringsproblemet löses med hjälp av kommersiell mjukvara, Gurobi. Vi använder även anonymiserad, filtrerad, resekortsdata för att modellera passagerarflöden och relevanta anslutningar. Den andra metoden omplanerar tågtrafiken utan hänsyn till annan kollektivtrafik och möjliggör en viktning (dvs. prioritering) av tåg med ett större antal avstigande resenärer. Här används en parallelliserad algoritm som på ett effektivt sätt ska kunna planera om tågen vid störningar baserat på ett antal kvalitetsindikatorer. Båda metoderna har tillämpats i datorbaserade experiment för störningarsscenarier på Blekinge Kustbana och anslutande banor.Resultat och slutsatserResultaten från projektet visar på vikten av att utforma beräkningsstöd för tågtrafikledning som inkluderar flera olika målkriterier och kvalitetsindikatorer vid omplaneringen av tåg vid störningar. Vilka kriterier och indikatorer som är mest relevanta att fokusera på i den operativa driften är en bedömning som bör göras dels utifrån ett användarperspektiv, dels baserat på gällande lagstiftning inklusive aktuella operativa regler definierade i järnvägsnätsbeskrivningen för innevarande år. Preliminära resultaten från studierna visar även på möjligheterna med att samordna den regionala tåg- och busstrafiken i större utsträckning än vad som är praktiskt möjligt idag. Tillgången till data ökar samt olika mer eller mindre avancerade digitala hjälpmedel för resenärer såväl som för trafikledning föreslås och diskuteras av branschen och inom forskarsamhället, men hur man uppnår en effektiv hantering av störningar och säkerställer ändamålsenlig trafikinformation till resenärer är först och främst en organisatorisk fråga, snarare än en teknisk utmaning.
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| 38. |
- Törnquist Krasemann, Johanna, 1977-, et al.
(författare)
-
Transform project deliverable D3.1 : A toolbox of real-time strategies for smart transfers
- 2017
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Organizing, financing and operating public transport service networks can be quite a challenge. The liberalization of the public transport sector within EU has introduced some additional challenges since the public transport systems nowadays more often consist of services operated by multiple organizations. When passengers move between public transport service networks that are operatedby different organizations, the need for effective coordination become evident. The importance of effective coordination and the associated challenge to achieve this – independent of organizational structure - is the point of origin for the TRANS-FORM project. The project focuses on the development of an integrated passenger-focused management approach that takes advantage of multiple datasources and state-of-the-art scheduling support.This document reports on the work performed in task 3.1 entitled “Real-time traffic management optimization” and task 3.2 entitled “Smart real-time strategies” of the TRANS-FORM project. These tasks were performed as part of work package 3 “Methods for Planning and Operating RobustServices”.The work in the mentioned tasks focus on how to model an integrated passenger-focused management approach including developing strategies that enable improved coordination and smooth passenger transfers. This document contains a specification of the configuration of each modelled level (hub,urban and regional) and the proposed types of management strategies as well as the requiredinformation flow. A specification of the proposed integration of those three levels and their interactionis also presented.Additional project documentation can be found on the project website: http://www.transform-project.org/index.php/progress-and-results/.
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| 39. |
- Törnquist Krasemann, Johanna, 1977-, et al.
(författare)
-
Trip Plan Generation using Optimization: A Benchmark of Freight Routing and Scheduling Policies within the Carload Service Segment
- 2012
-
Ingår i: Journal of Rail Transport Planning & Management. - : Elsevier. - 2210-9706 .- 2210-9714. ; 2:1-2, s. 1-13
-
Tidskriftsartikel (refereegranskat)abstract
- The rail freight carload service segment enables the distribution of freight volumes down to the unit of single rail cars, and stand as an important alternative to road transportation. However, this service segment is often associated with significant uncertainties and variations in daily freight volumes. Such uncertainties are challenging to manage since operating plans generally are established long in advance of operations. Flexibility can instead be found in the way trip plans are generated. Previous research has shown that a commonly used trip plan generation policy does not exploit the available flexibility to the full extent. In this paper, we therefore suggest an optimization-based freight routing and scheduling (OFRS) policy to address the rail freight trip plan generation problem. This OFRS-policy generates trip plans for rail cars while still restricted by the customer commitments. The policy involves a MIP formulation with a continuous time representation and is solved by commercial software. We apply the OFRS-policy on a case built on real data provided by the Swedish rail freight operator, Green Cargo, and assess the performance of the policy comparing the current industry practice. The results show that by using the OFRS policy, we can achieve a reduction in the total transportation times, number of shunting activities and potentially also a reduction in the service frequency given the considered transport demand.
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| 40. |
- Yap, Menno, et al.
(författare)
-
Quantification and control of disruption propagation in multi-level public transport networks
- 2022
-
Ingår i: International Journal of Transportation Science and Technology. - : Elsevier. - 2046-0430 .- 2046-0449. ; 11:1, s. 83-106
-
Tidskriftsartikel (refereegranskat)abstract
- Due to the multi-level nature of public transport networks, disruption impacts may spill-over beyond the primary effects occurring at the disrupted network level. During a public transport disruption, it is therefore important to quantify and control the disruption impacts for the total public transport network, instead of delimiting the analysis of their impacts to the public transport network level where this particular disruption occurs. We propose a modelling framework to quantify disruption impact propagation from the train network to the urban tram or bus network. This framework combines an optimisation-based train rescheduling model and a simulation-based dynamic public transport assignment model in an iterative procedure. The iterative process allows devising train schedules that take into account their impact on passenger flow re-distribution and related delays. Our study results in a framework which can improve public transport contingency plans on a strategic and tactical level in response to short- to medium-lasting public transport disruptions, by incorporating how the passenger impact of a train network disruption propagates to the urban network level. Furthermore, this framework allows for a more complete quantification of disruption costs, including their spilled-over impacts, retrospectively. We illustrate the successful implementation of our framework to a multi-level case study network in the Netherlands. © 2021 Tongji University and Tongji University Press
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| 41. |
- Zeeshan Iqbal, Syed Muhammad, et al.
(författare)
-
A Comparative Evaluation of Re-scheduling Strategies for Train Dispatching during Disturbances
- 2012
-
Konferensbidrag (refereegranskat)abstract
- Railway traffic disturbances occur and train dispatchers make re-scheduling decisions in order to reduce the delays. In order to support the dispatchers, good rescheduling strategies are required that could reduce the delays. We propose and evaluate re-scheduling strategies based on: (i) earliest start time, (ii) earliest track release time, (iii) smallest buffer time, and (iv) shortest section runtime. A comparative evaluation is done for a busy part of the Swedish railway network. Our results indicate that strategies based on earliest start time and earliest track release time have the best average performance.
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