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Törnquist Krasemann, Johanna
Publications (5 of 5) Show all publications
Andersson, E., Peterson, A. & Törnquist Krasemann, J. (2015). Improved Railway Timetable Robustness for Reduced Traffic Delays – a MILP approach. In: 6th International Conference on Railway Operations Modelling and Analysis, Tokyo, Mars 23-26, 2015.: . Paper presented at 6th International Conference on Railway Operations Modelling and Analysis - RailTokyo.
Open this publication in new window or tab >>Improved Railway Timetable Robustness for Reduced Traffic Delays – a MILP approach
2015 (English)In: 6th International Conference on Railway Operations Modelling and Analysis, Tokyo, Mars 23-26, 2015., 2015Conference paper, Published paper (Refereed)
Abstract [en]

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.

Keywords
Railway traffic, Timetabling, Robustness, Margin re-allocation, Punctuality, Optimization
National Category
Transport Systems and Logistics
Identifiers
urn:nbn:se:liu:diva-116651 (URN)
Conference
6th International Conference on Railway Operations Modelling and Analysis - RailTokyo
Projects
Robusta tidtabeller för järnvägstrafik
Available from: 2015-03-30 Created: 2015-03-30 Last updated: 2018-08-23Bibliographically approved
Andersson, E., Peterson, A. & Törnquist Krasemann, J. (2013). Introducing a New Quantitative Measure of Railway Timetable Robustness Based on Critical Points. In: 5th International Seminar on Railway Operations Modelling and Analysis - RailCopenhagen 2013: . Paper presented at 5th International Seminar on Railway Operations Modelling and Analysis, Copenhagen, May 13-15, 2013.
Open this publication in new window or tab >>Introducing a New Quantitative Measure of Railway Timetable Robustness Based on Critical Points
2013 (English)In: 5th International Seminar on Railway Operations Modelling and Analysis - RailCopenhagen 2013, 2013Conference paper, Published paper (Refereed)
Abstract [en]

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.

Keywords
Timetabling, robustness measures, railway traffic
National Category
Transport Systems and Logistics
Identifiers
urn:nbn:se:liu:diva-92712 (URN)978-87-7327-246-6 (ISBN)
Conference
5th International Seminar on Railway Operations Modelling and Analysis, Copenhagen, May 13-15, 2013
Available from: 2013-05-16 Created: 2013-05-16 Last updated: 2018-08-23
Andersson, E. V., Peterson, A. & Törnquist Krasemann, J. (2013). Quantifying railway timetable robustness in critical points. Journal of Rail Transport Planning & Management, 3(3), 95-110
Open this publication in new window or tab >>Quantifying railway timetable robustness in critical points
2013 (English)In: Journal of Rail Transport Planning & Management, ISSN 2210-9706, E-ISSN 2210-9714, Vol. 3, no 3, p. 95-110Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Elsevier, 2013
Keywords
Delay management; Railway traffic; Robustness measures; Timetabling
National Category
Transport Systems and Logistics
Identifiers
urn:nbn:se:liu:diva-106703 (URN)10.1016/j.jrtpm.2013.12.002 (DOI)
Available from: 2014-05-19 Created: 2014-05-19 Last updated: 2018-08-23Bibliographically approved
Törnquist Krasemann, J. & Backåker, L. (2012). Trip Plan Generation using Optimization: A Benchmark of Freight Routing and Scheduling Policies within the Carload Service Segment. Journal of Rail Transport Planning & Management, 2(1-2), 1-13
Open this publication in new window or tab >>Trip Plan Generation using Optimization: A Benchmark of Freight Routing and Scheduling Policies within the Carload Service Segment
2012 (English)In: Journal of Rail Transport Planning & Management, ISSN 2210-9706, E-ISSN 2210-9714, Vol. 2, no 1-2, p. 1-13Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Elsevier, 2012
Keywords
Railway transport, Freight transport, Optimization, Trip plan generation, Routing and scheduling
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-91506 (URN)10.1016/j.jrtpm.2012.06.001 (DOI)
Projects
Den Nationella Forskarskolan i Intelligenta TransportSystem
Available from: 2013-04-26 Created: 2013-04-26 Last updated: 2017-12-06Bibliographically approved
Andersson, E., Peterson, A. & Törnquist Krasemann, J. (2011). Robustness in Swedish Railway Traffic Timetables. In: S. Ricci, I.A. Hansen, G. Longo, D. Pacciarelli, J. Rodriguez, E. Wendler (Ed.), Railrome 2011: Book of Abstracts 4th International Seminar on Railway Operations Modelling and Analysis. Paper presented at 4th International Seminar on Railway Operations Modelling and Analysis, Sapienza - University of Rome,February 16-18, 2011.
Open this publication in new window or tab >>Robustness in Swedish Railway Traffic Timetables
2011 (English)In: Railrome 2011: Book of Abstracts 4th International Seminar on Railway Operations Modelling and Analysis / [ed] S. Ricci, I.A. Hansen, G. Longo, D. Pacciarelli, J. Rodriguez, E. Wendler, 2011Conference paper, Published paper (Other academic)
Abstract [en]

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.

Keywords
Railway traffic, Scheduling, Robustness, Delay management.
National Category
Transport Systems and Logistics
Identifiers
urn:nbn:se:liu:diva-79257 (URN)
Conference
4th International Seminar on Railway Operations Modelling and Analysis, Sapienza - University of Rome,February 16-18, 2011
Available from: 2012-07-05 Created: 2012-07-04 Last updated: 2018-08-23Bibliographically approved
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