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Optimization-Based Methods for Revising Train Timetables with Focus on Robustness
Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
2016 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2016. , 49 p.
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1763
National Category
Control Engineering Computational Mathematics Transport Systems and Logistics Signal Processing Computer Science
URN: urn:nbn:se:liu:diva-132920DOI: 10.3384/lic.diva-132920Local ID: liu-tek-lic 2016ISBN: 9789176856314 (print)OAI: diva2:1051321
2016-12-06, Täppan, TP2, Campus Norrköping, Linköpings Universitet, Norrköping, 10:15 (English)
Available from: 2016-12-01 Created: 2016-12-01 Last updated: 2016-12-05Bibliographically approved
List of papers
1. Robustness Improvements in a Train Timetable with Travel Time Dependent Minimum Headways
Open this publication in new window or tab >>Robustness Improvements in a Train Timetable with Travel Time Dependent Minimum Headways
2015 (English)Conference paper (Other academic)
Abstract [en]

In a railway network with dense traffic, trains’ scheduled arrival and departure times arehighly dependent on each other and even a small delay easily propagates to subsequenttrains using the same infrastructure resources. In the current paper a given timetable is comparedto a modified timetable, where the assigned minimum time slot in the traffic for aservice is linearly increasing with the service’s travel time. The underlying assumption isthat trains lose precision as they travel longer and catching a fixed-size time slot is easier atthe beginning of the journey. Real world observations confirm this assumption as well. Theaim of this study is to verify the improvement in the robustness of those timetables that aremodified with respect to the idea of travel time dependent reserved time slots for the arrivaltimes of trains and to compare the results with the initial timetables. Numerical experimentsare conducted on a selected double track segment of the Swedish Southern mainline. Fourtimetable case studies are considered for the experiments: off-peak hours and peak hoursin 2011 and 2014, respectively. Each timetable is tested for various disturbance scenarios.Several performance measures are used to evaluate delay propagation in the timetables, includingdeviations from the initial timetable, total delays, total number of delayed trains atdestinations, number of punctual trains with 5 minutes arrival delay tolerance at destinationsand number of violations in trains’ overtaking orders. Results show that the modifiedtimetables outperform the initial ones for small disturbances.

Robustness, Railway Timetable, Ex-post measures, Delay propagation, Performance measures
National Category
Transport Systems and Logistics
urn:nbn:se:liu:diva-117042 (URN)
6th International Conference on Railway Operations Modelling and Analysis - RailTokyo2015, Tokyo, March 23-26, 2015
Available from: 2015-04-13 Created: 2015-04-13 Last updated: 2016-12-01

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Khoshniyat, Fahimeh
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