2 Search Results for "Törnquist, Johanna"


Document
Analysis of Strengths and Weaknesses of a MILP Model for Revising Railway Traffic Timetables

Authors: Fahimeh Khoshniyat and Johanna Törnquist Krasemann

Published in: OASIcs, Volume 59, 17th Workshop on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2017)


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.

Cite as

Fahimeh Khoshniyat and Johanna Törnquist Krasemann. Analysis of Strengths and Weaknesses of a MILP Model for Revising Railway Traffic Timetables. In 17th Workshop on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2017). Open Access Series in Informatics (OASIcs), Volume 59, pp. 10:1-10:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)


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@InProceedings{khoshniyat_et_al:OASIcs.ATMOS.2017.10,
  author =	{Khoshniyat, Fahimeh and T\"{o}rnquist Krasemann, Johanna},
  title =	{{Analysis of Strengths and Weaknesses of a MILP Model for Revising Railway Traffic Timetables}},
  booktitle =	{17th Workshop on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems (ATMOS 2017)},
  pages =	{10:1--10:17},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-95977-042-2},
  ISSN =	{2190-6807},
  year =	{2017},
  volume =	{59},
  editor =	{D'Angelo, Gianlorenzo and Dollevoet, Twan},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.ATMOS.2017.10},
  URN =		{urn:nbn:de:0030-drops-78995},
  doi =		{10.4230/OASIcs.ATMOS.2017.10},
  annote =	{Keywords: Railway, Timetable, Short term planning, Boosting Methods, Valid inequalities}
}
Document
Computer-based decision support for railway traffic scheduling and dispatching: A review of models and algorithms

Authors: Johanna Törnquist

Published in: OASIcs, Volume 2, 5th Workshop on Algorithmic Methods and Models for Optimization of Railways (ATMOS'05) (2006)


Abstract
This paper provides an overview of the research in railway scheduling and dispatching. A distinction is made between tactical scheduling, operational scheduling and re-scheduling. Tactical scheduling refers to master scheduling, whereas operational scheduling concerns scheduling at a later stage. Re-scheduling focuses on the re-planning of an existing timetable when deviations from it have occurred. 48 approaches published between 1973 and 2005 have been reviewed according to a framework that classifies them with respect to problem type, solution mechanism, and type of evaluation. 26 of the approaches support the representation of a railway network rather than a railway line, but the majority has been experimentally evaluated for traffic on a line. 94 % of the approaches have been subject to some kind of experimental evaluation, while approximately 4 % have been implemented. The solutions proposed vary from myopic, priority-based algorithms, to traditional operations research techniques and the application of agent technology.This paper provides an overview of the research in railway scheduling and dispatching. A distinction is made between tactical scheduling, operational scheduling and re-scheduling. Tactical scheduling refers to master scheduling, whereas operational scheduling concerns scheduling at a later stage. Re-scheduling focuses on the re-planning of an existing timetable when deviations from it have occurred. 48 approaches published between 1973 and 2005 have been reviewed according to a framework that classifies them with respect to problem type, solution mechanism, and type of evaluation. 26 of the approaches support the representation of a railway network rather than a railway line, but the majority has been experimentally evaluated for traffic on a line. 94 % of the approaches have been subject to some kind of experimental evaluation, while approximately 4 % have been implemented. The solutions proposed vary from myopic, priority-based algorithms, to traditional operations research techniques and the application of agent technology.

Cite as

Johanna Törnquist. Computer-based decision support for railway traffic scheduling and dispatching: A review of models and algorithms. In 5th Workshop on Algorithmic Methods and Models for Optimization of Railways (ATMOS'05). Open Access Series in Informatics (OASIcs), Volume 2, pp. 1-23, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2006)


Copy BibTex To Clipboard

@InProceedings{tornquist:OASIcs.ATMOS.2005.659,
  author =	{T\"{o}rnquist, Johanna},
  title =	{{Computer-based decision support for railway traffic scheduling and dispatching: A review of models and algorithms}},
  booktitle =	{5th Workshop on Algorithmic Methods and Models for Optimization of Railways (ATMOS'05)},
  pages =	{1--23},
  series =	{Open Access Series in Informatics (OASIcs)},
  ISBN =	{978-3-939897-00-2},
  ISSN =	{2190-6807},
  year =	{2006},
  volume =	{2},
  editor =	{Kroon, Leo G. and M\"{o}hring, Rolf H.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/OASIcs.ATMOS.2005.659},
  URN =		{urn:nbn:de:0030-drops-6592},
  doi =		{10.4230/OASIcs.ATMOS.2005.659},
  annote =	{Keywords: Decision support, railway traffic scheduling, railway traffic dispatching, overview}
}
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